HES No. 4

Introduced around 1965 and made by Ericsson (ETL).

HES 4 diagrams (ZIP)

HES 4 circuit diagrams (PDF)

An article from the Ericsson Bulletin

Descriptive Leaflet

TELECOMMUNICATIONS INSTRUCTION
C MARKETING INSTALLATION
3 Internal
C3031
Issue 2, Sept 1973

HOUSE EXCHANGE SYSTEM No. 4
Facilities

1 GENERAL
This Instruction describes the facilities provided in a House Exchange System No. 4 (HES No. 4) which has been given the sales name Keymaster 2 + 10. This system provides inter-communication between stations with direct access from these stations to exchange lines.

2 DEFINITIONS
Multiple Station
A multiple station is one equipped with a Telephone, Intercom No. 4/.... which is an instrument based on the 700 type telephone design. Multiple stations are linked by a multiple cable and are normally confined to one building but the cable may be extended to stations in nearby buildings, if signalling limits are not exceeded.

Non-Multiple Extension
This is an extension station connected to the multiple by a two-wire line and a relay-unit. The extension is equipped with a Telephone No. 710 (F or CB).

Main Station
This is the multiple station where incoming calls always give an audible signal and which assists non-multiple extensions with calls to other stations. A small key unit is required to be sited with the Telephone Intercom No. 4/1 at this station when non-multiple extensions are provided. The main station also controls some of the additional facilities which may be added to the system. One other multiple station may be designated 2nd choice main station if required.

3 CAPACITY OF INSTALLATION
A HES No. 4 comprises two exchange lines and up to ten stations; exceptionally, one additional multiple station can be provided. A total of four non-multiple extensions or private circuits may be fitted in lieu of four multiple stations. The system also includes a Power-Unit No. 52A and an exchange line relay-unit, together with a relay-unit for each non-multiple extension or private circuit that has been provided; these units are all wall mounted.

4 EXTENSION PLAN ARRANGEMENTS
Extension Plans 1, 1A and 4 internal only, may be provided at a non-multiple extension, if the appropriate limits given in C3010 are not exceeded at the most remote instrument of the extension plan.

Extension telephones cannot be associated with multiple stations, and it is not possible to work two multiple station telephones in parallel.

5 CONNECTION TO PUBLIC EXCHANGE
The HES No. 4 works on CB principles but may be connected to any type of public exchange. In CBS and LB areas, an auxiliary unit must be fitted in the exchange lines to provide the necessary CB conditions.

The HES No. 4 is not suitable for shared service.

6 LAMP SIGNALS
Telephones, Intercom, No. 4/.... are equipped with four lamps. The lamp adjacent to each exchange line press-button glows at all stations when that exchange line is in use. The appropriate lamp at the right-hand end of the station identification label glows only at the station which is engaging the line.

7 EXCHANGE CALLS
(a) Incoming to System
Incoming exchange calls are signalled visually at all multiple stations, except those prohibited exchange line service, by lamps which are adjacent to the press-buttons of the exchange lines. At all stations, the lamp associated with the line on which the call is being received flashes in sympathy with the ringing, then glows steadily when the call is answered.

All Telephones, Intercom, No. 4/.... are fitted with standard magneto bells and up to five bells in series may be rung simultaneously from the public exchange except where the ringing supply is from a low-power source, e.g. a vibrator, when only one or two bells may be rung; see also para 13.

For incoming exchange call ringing at non-multiple extensions see paragraph 9.

(b) Incoming to Private Circuit
In special instances incoming exchange calls may be extended to private circuits (see (b) and paragraph 11).

(c) Outgoing from Multiple Stations
Direct connection to the public exchange from any multiple station with full facilities is obtained by pressing the press-button of the selected exchange line. The lamp adjacent to the press-button glows at all stations to indicate that the line is engaged and the appropriate lamp at the right-hand end of the station identification label glows at the engaging station. Exchange calls are normally secret (see (k)).

(d) Outgoing from Non-Multiple Extension
Direct connection to the exchange from any non-multiple extension with full facilities is obtained by pressing the EXCH button in the Telephone No. 710. Selection of the line to be used is determined automatically by the relay-unit which connects the extension to the multiple cable.

(e) Exchange Service Restriction or Prohibition
Access to the exchange lines may be restricted at selected multiple stations and non-multiple extensions, so that calls may be originated or received under the control of the main station only. Exchange service may be prohibited to selected multiple stations and non- multiple extensions.

(f) Main Station Control
Incoming exchange calls intended for non-multiple extensions or private circuits can only be transferred to these extensions via the main station. The main station also controls the transfer of an exchange call from a non-multiple extension to another non-multiple extension, multiple station, or private circuit. It is not possible for a private circuit to transfer an exchange call. The main station also controls exchange service to stations with restricted facilities.

(g) Transfer Facility
An incoming or outgoing exchange call may be transferred from one multiple to another, or from a non-multiple extension via the main station to another non-multiple extension or multiple station without releasing the exchange connection.

On installations with two exchange lines, a multiple station may hold a call on one exchange line while transferring a call incoming on the other line. The main station must assist in the transfer of exchange calls to or from non-multiple extensions or multiple stations with restricted facilities. During the transfer of an exchange call from one multiple station to another, the change of the exchange line lamp from flashing to a steady glow indicates that the receiving station is ready to accept the call. Pressing the exchange line release R button at the transferring station completes the transfer of the call, and this may be visually confirmed by the station engaging lamp, which dims at the transferring station and glows at the receiving station when transfer has occurred.

(h) Hold Facility
Any multiple station may hold an exchange call while making an intercom call to another station on the system. In the exchange line hold condition, the subscriber on the exchange line cannot hear the conversation between the holding station and the called station. On installations with two exchange lines, any multiple station with full facilities may hold one exchange line while making a call on the other exchange line. During the holding of an exchange line its line engaged lamp, adjacent to the exchange line press-button, will flash at all stations two or three times per second.

(j) Exchange Line Engaged
At multiple stations the lamps adjacent to the exchange line press-buttons provide a visual indication when the line is engaged. The exchange line press-button must not be operated when its associated lamp is glowing; to do so may cut off an established call. The lamps adjacent to the conference press-button, i.e. at the right-hand end of the station identification label, provide a visual indication as to when a station is engaging the exchange line, the lamp glowing only at the engaging station.

(k) Secrecy and Monitoring
Exchange calls are normally secret but a monitoring facility may be given to the main or other selected multiple station. This facility is restricted to one station at any installation and is not for continuous use as it degrades transmission.

8 LOCAL INTERCOMMUNICATION CALLS
(a) Multiple Stations
There is direct calling between all multiple stations on the system.

Independent calls between stations in pairs, up to the capacity of the system may proceed simultaneously without mutual interference, but they are not secret and a station may break in by calling one of the engaged stations.

(b) Calling a Station Engaged on an Exchange Call
At a calling multiple station a buzzer signal is normally given if the called multiple station is engaged on, or holding, an exchange line
(see (c)).

If the called station is a non-multiple extension the buzzer signal is given only when the exchange line is engaged speaking, not during hold conditions.

Private circuits cannot hold or transfer exchange calls, and a buzzer signal will always be received when a private circuit is engaged on an exchange line call.

(c) To Allow a Multiple Station to Call a Multiple Station Engaged on an Exchange Call
The facility may be given whereby a multiple station may be called while it is engaged on an exchange call. The called station then answers the intercom call by pressing its own station calling press-button. This facility cannot be provided that installations consisting of eleven stations as a multiple station's own calling press-button is no longer available to answer the calling station. Stations with the facility of being called while engaged on an exchange line do not return an engaged signal to calling stations.

(d) Multiple Station Calling Non-Multiple Extension or Private Circuit
There is direct calling from all multiple stations to any non-multiple extension or private circuit. Calls at the non-multiple extension are answered by operating the EXTN press-button.

(e) Non-Multiple Extension Calling Multiple Station
A non-multiple extension wishing to call a multiple station first calls the main station by pressing the EXTN button fitted in the Telephone No. 710. The main station then asks the required multiple station to call the non-multiple extension.

(f) Non-Multiple Extension Calling Non-Multiple Extension or Private Circuit
A non-multiple extension wishing to call another non-multiple extension or private circuit first calls the main station by pressing the EXTN press-button fitted in the Telephone No. 710. The main station then calls the required extension or private circuit and completes the connection via a connect circuit at the main station. The call must be released by restoration of the connect keys on receipt of a clear signal from each of the extensions or circuits.

(g) Private Circuit Calling Multiple Station
The private circuit calls the main station which then asks the required multiple station to call the private circuit, i.e. the call is reverted.

(h) Private Circuit Calling Non-Multiple Extension or Private Circuit
The private circuit first calls the main station and the procedure is then the same as described in (f).

(j) Conference Calls
Any multiple station may call all, or any number of other multiple stations, non-multiple extensions and private circuits, and then speak to them simultaneously. This facility is not available on incoming or outgoing exchange calls.

Any non-multiple extension or private circuit, with the assistance of the main station may call all, or any number of other multiple stations, non-multiple extensions and private circuits, and then speak to them simultaneously.

9 NIGHT SERVICE TO NON-MULTIPLE EXTENSIONS
An individual or number of non-multiple extensions may be given night service by means of a key at the main station. The incoming exchange call is then extended to ring the bell at a non- multiple extension. It can be arranged that one selected line only, or both lines are signalled at a particular non-multiple extension.

Exchange service continues to be available at all stations and intercom calls are not affected by night service conditions.

10 NIGHT SERVICE TO PRIVATE CIRCUITS
When the facility is allowed, a private circuit may be given night service for incoming calls only by switching at the main stations. The incoming exchange line ringing is then extended over the private circuit. Exchange service is not affected at multiple stations and non- multiple extensions when a private circuit is on night service. Intercom calls between multiple stations and non-multiple extensions are not affected, but a private circuit on night service cannot be included.

11 ASSOCIATION WITH A PBX
A HES No. 4 installation may be associated with a PBX in several ways.

(a) An extension from a PBX may be connected as an exchange line at the HES No. 4. All facilities available to PBX extensions including operator recall, are also available to HES No. 4 stations. Mixed connections i.e. one exchange line and one PBX extension, are not permitted on installations with non-multiple extensions, due to line identification difficulties on outgoing calls from these extensions.

(b) Subject to satisfactory transmission, a HES No. 4 non-multiple extension may be terminated as an exchange line or private circuit on the distant switchboard. Exchange calls can be extended only from the HES No. 4.

(c) A Relay-Unit Q524 fitted in place of a multiple station and terminated at the PBX as an extension will usually provide all normal inter-switchboard facilities between a HES No. 4 and a PBX.

(d) An HES No. 4 installation may be connected to another HES by private circuit, using a Relay-Unit Q524 fitted in place of a multiple station. The extension of exchange calls over a connecting circuit is not normally allowed.

13 EXTENSION BELLS AND BUZZERS
Extension magneto bells may be provided in lieu, or in addition to, the instrument bell at multiple stations. The total number of bells. to be rung simultaneously from the public exchange must not exceed five, except where the ringing supply is from a low-power source when only one or two bells may be rung. In special circumstances alternative ringing arrangements may be used; these sometimes include the use of a local ringing converter.

One additional magneto bell may be provided at a non-multiple station for intercom signalling purposes.

Loud sounding bells or buzzers may also be provided (see C3036).

14 TELEPHONES WITH HEARING-AID HANDSET
The Handset No. 4 should be used to provide hearing-aid facilities when required at multiple stations and non-multiple extensions.

15 STD FACILITIES
Meters No. 19 may be fitted to the exchange lines (see C3036).

Formerly EI Telephones, Stations, Q1015

TELECOMMUNICATIONS INSTRUCTION
C MARKETING INSTALLATION
3 Internal
C3032
Issue 2, Sept 1973

HOUSE EXCHANGE SYSTEMS Nos. 3 AND 4
Description of Equipment

1 SCOPE OF INSTRUCTION
This Instruction describes the various items of equipment used on the House Exchange Systems (HES) Nos. 3 and 4. The definitions of terms and facilities for the HES No. 3 are described in C3030 and for the HES No. 4 in C3031. Installation of the HES No. 3 is described in C3034 and the HES No. 4 in C3036.

3 TELEPHONE, INTERCOM, No. 3/1
This telephone is used at a HES No. 3 installation which caters for one exchange line and up to five stations. The telephone is basically a Telephone No. 710 and has a cover (Part 6/DCO/627)which is provided with two lenses; it is fitted with a self-locking BELL OFF button in position A, an EXCH button in position B and two split buttons in each of positions C and D.

The moulded base (a standard item) is fitted with a special gravity switch and has been coded Part 4/DBA/107.

Fitted between the gravity-switch pillars in a sub-assembly known as a Switch Composite, No. 1A, which consists of a spring contact unit wired to a Strip, Connection, No. 155B, the assembly having seven flexible spade-ended leads for connection to the telephone circuit. The contact unit is held in position between the gravity-switch pillars by four screws and the connection strip is held at the rear of the pillars by two locating pins and a spring clip.

The plungers and spring contacts located in positions C and D of the latch- plate assembly form the intercom signalling circuits. The spring contacts and plunger in position B are contacts KX of the exchange line circuit, and these may be released either by replacing the handset or by pressing any one of the four buttons in positions C and D. The spring contacts in position A which are adjacent to position B, are contacts KH and these also operate when contacts KX are operated, but they can only be released by replacing the handset; these form the hold circuit of the exchange line. The remaining spring contacts in position A control the magneto bell cut-off or additional facilities. These springs are operated by a special plunger which is fixed to the latch plate by a bracket. The spring assembly is illustrated in Diagram Q 422 and the button arrangement is shown in Diagram Q 424.

Fixed on the sides of the gravity-switch pillars are two Lamp-fittings, No. 16 (incomplete); viewed from the front of the telephone, the fitting on the left-hand side contains a Lamp No. 26H which provides the red lamp signals for the exchange line, whilst in the fitting on the right-hand side is a Lamp No. 26i which provides the engaged signal for the intercom circuit.

The d.c. buzzer for intercom calling is fitted onto the cord grommet frame and the complete assembly has been coded Buzzer No. 2B-2.

The telephone is fitted with a Cord, Inst, No. 20/03AJ, ..., 72in which is terminated with the multiple cables onto a Block, Terminal, No. 37.

The telephone is normally fitted with a Handset No. 3. The CB telephone has a Dial, Auto, Dummy, No. 6A, The complete circuit of the telephone is shown in Diagram Q 422 and the wiring of the Switch, Composite, No. 1A only in Diagram Q 423. The instrument cord and cable connections for the telephone are shown in Diagram Q 424.

The telephone is available in black, grey and ivory.

4 TELEPHONE, INTERCOM, No. 4/1
This telephone is used at a HES No. 4 installation which caters for one or two exchange lines and up to ten stations (exceptionally eleven stations).

The telephone mechanism is mounted on a metal base and is enclosed by a moulded plastic cover (Part 1/DCO/683).

The telephone when issued is fitted with a Handset No. 3 and a Connector No. 1046A. The overall dimensions of the telephone are approximately 11.25in (285mm) x 6.75in (170mm) x 4.75in (120mm) high.

Above the front sloping face of the cover containing the dial aperture, is an almost horizontal face in which is a rectangular aperture for the press-buttons of the key unit. Over the rectangular aperture and surrounding the press-buttons is a separate escutcheon which is sprung into place and clips onto the metal face of the key unit. This escutcheon contains the station identification labels with their clear plastic covers and the lenses for the exchange line lamps.

The labels and plastic covers are removed by pressing at the end of the plastic cover with the blunt end of a pencil or similar object; this causes the middle to bow upwards where the cover and label may be gripped and pulled gently upwards. If the label does not rise with the cover it may be eased up by inserting a pin at the middle by the side of the label and levering gently upwards. The escutcheon is removed by inserting a thin blunt edged blade, or finger tip under the chamfered edge at the back and springing off the rear clip, then lifting upwards to release the front spring clip. In front of the handset rest there is provision for four press-buttons which are used to control the bell cut-off facility and any additional facilities that may be provided.

The telephone cover is fixed by two screws in the handset rest and by a screw in the front of the dial mounting.

The press-buttons are in two rows, from left to right there are the two ivory exchange line buttons engraved 1 or 2, two smaller ivory exchange line release buttons engraved R; ten grey press-buttons for signalling and speaking to other stations over the intercom circuits, and the single ivory conference button engraved C.

At the front of the base are two bell gongs, over which Relay-units Q 527 and Q 528 (see paragraphs 18 and 19) may be mounted as required. The magneto bell is a Bell No. 59A with long flexible leads and has been coded Bell No. 59A-2.

Behind the bell and across the base is a printed circuit board with the components of a standard 700-type telephone transmission circuit.

The key unit is in two parts; a metal frame carrying spring-sets for the exchange lines and intercom circuits, and a press-button assembly.

The metal frame screwed to the base of the telephone, carried on each side, the spring assembly of an exchange line and a printed board with spring contacts riveted to it, for intercom signalling and speaking.

At the end of the frame near the exchange line spring contacts is a plunger assembly which operates on second and subsequent overpresses of an exchange press-button. The plunger operates a spring-set to provide operator-recall facility to either exchange line circuits. A second spring assembly inside the frame operates when the station press-buttons are overpressed and provides the intercom signalling condition.

At the end of the frame near the conference button are a number of `polytags' carrying resistors associated with lamp circuits etc.

On the top, near each of the four corners of the frame, is a lug which carries a Lamp-fitting No. 19 and a Lamp No. 41E. The press-button mechanism is held in the frame by a countersunk screw at each corner of the top plate.

On the left-hand side of the base, beneath the dial mounting, is a metal bracket which carries a d.c. buzzer (Buzzer No. 2B-3) for intercom calling.

Behind the key unit frame is a 72-way double-sided terminal block. On the top side is the telephone wiring; both soldered and screwed terminations. The instrument cord, a Connector No. 1046A, and any straps that may be required are terminated on the underside and these terminals are exposed by removing a cover plate from the base.

Over the cord entries at the rear of the base is a metal bracket which carries the intercom transmission feed coil and its associated resistors and capacitor.

The telephone is connected to the multiple cabling via a Box, Connection, No. 6A. The circuit and connector connections of the telephone are shown in Diagram Q 540.

The telephone is available in black, grey and ivory.

The weight of the complete instrument is 8.1lb.

TELEPHONE, INTERCOM, No. 4/1 with case removed
 

TELEPHONE, INTERCOM, No. 4/1 with base plate removed and wiring terminals exposed

5 BLOCK, TERMINAL, No. 37...
The Block, Terminal, No. 37... is used at HES No. 3 installations to terminate the multiple cables and Telephone, Intercom, No.3/1 at multiple stations. It is also used with a Control-unit Q 535 (see par 21) at a HES No. 4 installation.

The Block Terminal, No. 37... consists of a moulded plastic base (Part 1/DBA/99) on which is mounted a terminal block (Part 1/DBL/91), containing 25 double-sided screw terminations the tablet and base being enclosed by a moulded plastic cover (Part 1/DCO/62.5). At one end of the cover is a cut-out for cord entry and at the other end are three knockouts for cable entry.

The base has been modified to include a hole for back entry of cable and fixing holes for mounting the Block, Terminal, No. 37... over square type conduit outlet boxes, i.e. standard outlet boxes with 2.75in (70mm) fixing centres.

6 BOX, CONNECTION, No. 6A
The Box, Connection, No. 6A has a base area of approximately 6.25in (160mm) x 5.75in (145mm) and is nearly 2in (50mm) high.

Mounted on the metal base is a Connector No. 203B55B,, which is a 55-pin plug. Also fixed to the base on raised pillars are two 28-way terminal blocks (Part 1/DST/861). The inserts of the terminal blocks have screw terminals for multiple cabling on the front side, and solder terminals on the rear side which are wired to the pins of the Connector No. 203B55B. At the side of the connector is a bracket to retain the grommet of the telephone instrument cord (Connector No. 1046A). Also in the base is a hole for back entry of cables.

The grey moulded plastic cover is held on by two fixing screws, and the sides contain knockouts for cable entry and a cut-out for the cord entry. Details of the wiring between the connector and terminal tablets are given in Diagram Q(L) 510.

Box Connection No. 6A

7 BOX, CONNECTION, No. 7A
The Box, Connection, No. 7A is identical in size and shape to the Box, Connection, No. 6A. The metal base of the Box, Connection, No. 7A provides mounting on raised pillars for three 28-way double-sided terminal tablets (Part 1/DST/861). These tablets have screw terminals on front and rear sides. There is no provision in the base for back entry of cables. The sides of the moulded plastic cover contain knockouts for cable entry. Typical uses of the Box, Connection No. 7A are shown in Diagram Q 508.

8 WALL-MOUNTED RELAY-UNITS
Two sizes of metal case have been introduced for use with HES No. 3 and No. 4.

Relay-unit Q 405 is contained in a Case No. 131... which has a mounting surface of 12ins (305mm) x 4.5ins (110mm). All other wall-mounted units are contained in Case No. 133... which has a mounting surface of 12in (305mm) x 8.75in (220mm). Both cases extend 7.25in (185mm) from the mounting surface.

Circuit components are mounted on a metal plate which is hinged to the baseplate and the wiring form from the components is terminated on a connection strip, which is fixed to the baseplate. Cable entry is via a hole fitted with a grommet in the baseplate.

A clear space of 6ins (152mm) must be allowed on the left side of the units when fixing to the mounting surface. This space allows full movement of the hinged plate, with access to the wiring of the relays etc.

A description of each wall-mounted relay-unit is given in paragraphs 9 to 14.

9 RELAY-UNIT Q 405
Relay-unit Q 405 is provided at HES No. 3 installations which have multiple stations only. The unit contains the circuits which control the lamp signals in the Telephone, Intercom, No. 3/1, and the transmission feed relay for the intercom circuit. The wiring of the unit and the multiple cable terminate on a connection strip (Part 1/SST/71) the cable being connected to the screw terminals.

Wiring details are shown in Diagram. Q 405 and in Diagram ID 174, which is pasted inside the cover.

.Cable connections are shown in Diagrams Q 403 and Q 404.

When a HES No. 3 is working subsidiary to a switchboard with a low-power ringing source, it may be necessary to provide a local ringing supply, the output of which is controlled by relay contact RG2. Diagram Q 417 shows details of alternative ringing arrangements when working a HES No. 3 subsidiary to a switchboard or when more than 'five bells are to be rung.

The complete unit weighs approximately 5lb. (2.5kg).

10 RELAY-UNIT Q 410
Relay-unit Q 410 replaces Relay-unit Q 405 at HES No. 3 installations when a non-multiple extension is required. In addition to the components and circuits of the Relay-unit Q 405, the Relay-unit Q 410 also contains the components and circuits which connect the two-wire line of a non-multiple extension to the multiple wiring of the system.

In this unit there is no spare contact on relay RG, and when a HES No. 3 with a non-multiple extension is worked subsidiary to a switchboard which has a low-power ringing source, it will be necessary to change relay RG. The relay should be changed for a Relay No. 9871, and the additional contact wired as shown in Diagram Q 417, which gives details of alternative ringing arrangements. The relay RG must also be changed and wired to Diagram Q 417, when more than five magneto bells are to be rung at any installation.

The unit wiring and the multiple cable are terminated on a connection strip (Part 1/SST/71), with the cable connected to the screw terminals.

Wiring details of the Relay-unit Q 410 are shown in Diagram Q 410 and in Diagram LD 175, which is pasted inside the cover.

The complete unit weighs approximately 14lb. (6.3kg).

11 RELAY-UNIT Q 415
The Relay-unit Q 415 is provided when an inter-switchboard or private circuit is included in a HES No. 3 installation, and is fitted in addition to Relay-unit Q 405 or Q 410.

Relay-unit Q 415 contains a number of circuit elements, which may be strapped according to the type of signalling being used on the circuit.

The wiring details of Relay-unit Q 415 are shown in Diagram. Q 415 and in Diagram ID 180, which is pasted inside the cover.

The connections required when using the Relay-unit Q 415 are shown in Diagrams Q 441 to Q 447. Signalling limits for this unit are the same as for a Unit, Auxiliary Apparatus, No. 97 and are given in P1061.

The unit wiring and multiple cables together with the required strappings shown in Diagram Q 441 are terminated on two Strips, Connection, No. 121D mounted back to back; these are all soldered connections.

The complete unit weighs approximately 15lb. (6.8kg).

12 RELAY-UNIT Q 516
The Relay-unit Q 516 is fitted to all HES No. 4 installations, and contains the components and circuits which control the lamp signals and exchange line ringing signals at a Telephone, Intercom, No. 4/1 fitted at a multiple station. Relay contacts within the unit are also available, when required, to extend signal and start conditions to the relay-unit of non-multiple extensions or private circuits.

Current through each of the series connected exchange line engaged lamp circuits of a Telephone, Intercom, No. 4/1 is controlled by a transistor circuit. The transistor is mounted on a heat sink which also carries the associated resistors, capacitor and rectifier; this complete assembly has been coded Regulator No. 4A.

The Regulator No. 4A is fixed by two screws to the hinged plate and joined to the circuit by three flexible spade-ended leads. Care must be taken to ensure that these leads are correctly connected otherwise the transistor may be seriously damaged. The regulator is adjusted during manufacture to pass 104mA (- or + 12 ma) under load conditions, and should any component become faulty, the complete regulator must be changed.

Mounted on the baseplate of the relay-unit is a clip to hold a Connector No. 203C55C, which is a 55-way connector that has been provided with a number of straps between certain sockets, and is intended for use at multiple stations where a Telephone, Intercom, No. 4/1 has been disconnected for repair or replacement. By replacing the telephone socket with a Connector No. 203C55C the series circuits of the installation are maintained and service is continued at all other stations. The connections provided in the Connector No. 203C55C are shown in Diagram Q 510.

Wiring details of the Relay-unit Q 516 are shown in Diagram Q 516 and in Diagram LD 192, which is pasted in the cover.

The complete unit weighs approximately 12lb. (5.4kg).

Relay-Unit Q516 - Internal view

13 RELAY-UNIT Q 519
The Relay-unit Q 519 is provided at a HES No. 4 installation to connect the two-wire line of a non-multiple extension to the multiple wiring.

Circuits in the unit provide the non-multiple extension with most of the facilities of a multiple station; these facilities are fully described in C3031.

A Strip, Connection, No. 121M provides the terminating point for the unit wiring, multiple cables and strappings as required. Straps that may be needed should be connected on the permanent wiring side of the Strip, Connection, No. 121M; and the multiple cables terminated on the opposite side.

Details of the wiring are shown in Diagram Q 519 and in Diagram LD 195, which is pasted inside the cover.

When a Relay-unit Q 519 is provided, a Control-unit Q 535 or Q 537 (see para's 21 and 22) is always fitted at the main station and the operation of the Relay-unit Q 519 should be studied in conjunction with the operation of the Control-unit Q 535 or Q 537. Circuit elements and explanatory, notes are shown in diagrams in the Q 5... series.

The complete unit weighs approximately 17 lb. (7.7 kg).

14 RELAY-UNIT Q 524
The Relay-unit Q 524 is provided at a HES No. 4 installation to connect the two wires of a private circuit to the multiple wiring.

The unit contains circuit elements which may be connected by strappings on the Strip, Connection, No. 121M, to terminate the circuit at the HES No. 4 according to the type of signalling to be used. The cable connections and straps required for various signalling groups are shown in Diagrams Q 561 to Q 567.

Wiring details of the unit are shown in Diagram Q(L) 524 and in Diagram LD 194, which is pasted inside the cover.

Signalling limits for the Relay-unit Q 524 are the same as for a Unit, Auxiliary Apparatus, No. 97 and these are shown in P1061.

Straps should be connected on the permanent wiring side of the Strip, Connection, No. 121M and cabling should be terminated on the opposite side.

The complete unit weighs approximately 17 lb. (7.7 kg).

15 RELAY-UNITS MOUNTED IN TELEPHONES, INTERCOM
Certain facilities that are available to both HES No. 3 and No. 4 installations are provided by fitting small relay-unit into a Telephone, Intercom, No. 3/1 or No. 4/1 and modifying the instrument cord connections.

These units consist of a Relay No. 16/... or Relay No. 23/6 mounted on a metal mounting plate which is secured over a bell gong.

Other components may also be included, terminated on `polytags' pressed into the metal mounting plate.

The various relay-units for fixing inside Telephones, Intercom, are described in para's 16 to 19.

16 RELAY-UNIT Q 408
The Relay-unit Q 408 is provided in a Telephone, Intercom, No.3/1 when the instrument is to have restricted exchange service.

The unit consists of a Relay No. 16/1 and two diodes (Valves, Electronic, CV 7040) on a mounting plate (Part l/DMO/102), and has spade-ended flexible leads for connection to the telephone circuit.

Diagram Q 408 shows the wiring of the unit and the connections within the telephone.

17 RELAY-UNIT Q 409
The Relay-unit Q 409 is provided in a Telephone, Intercom, No.3/1 when the instrument is to have monitoring facilities.

The unit consists of a Relay No. 1612 wired with spade-ended flexible leads on a mounting plate (Part 2/DMO/102).

Diagram Q 409 shows the wiring of the unit and the connections within the telephone. Relay-Units No. 408 and 409 are mounted over the right-hand side bell gong.

18 RELAY-UNIT Q 527
The Relay-unit Q 527 is fitted in a Telephone, Intercom, No.4/1 when the station is to have restricted exchange service.

When exchanges service restriction applies to only one line the Relay-unit Q 527 should be used and connected to the appropriate line. When both lines are to be restricted the Relay-unit Q 527 should be connected to the line on position one of the telephone and a Relay-unit Q 528 (see par 19) connected to the line on position two.

The Relay-unit Q 527 consists of a Relay No. 16/1 and two rectifiers (Valves, Electronic, CV 8308) on a mounting plate (Part 3/DMO/102), and has flexible spade-ended leads for connection to the telephone. Details of the wiring and telephone connections are given in Diagram Q 527. The Relay-unit is mounted over the left-hand side bell gong.

19 RELAY-UNIT Q 528
The Relay-unit Q 528 is fitted in a Telephone, Intercom, No. 4/1 when both lines are to have restricted exchange service. The unit includes a mounting plate (Part 1/DMO/102) for mounting over the right-hand side bell-gong but in all other respects the Relay-unit Q 528 is identical to the Relay-unit Q 527. Details of the Relay-unit Q 528 are included in Diagram. Q 527.

20 TWO-WIRE CIRCUIT CONTROL-UNITS AT MAIN STATIONS
When a non-multiple extension or private circuit is fitted at a HES No. 4 installation a control-unit must be fitted at the main station. This unit provides the circuit calling and clearing supervisory, and exchange line testing circuits. There are two sizes of control-unit, Control-unit Q 535 which caters for one circuit and is described in par 21, and Control-unit Q 537, which caters for up to four circuits and is described in par 22.

21 CONTROL-UNIT Q 535
The Control-unit Q 535 is a desk unit measuring approximately 3.5in (90mm) wide x 5.5in (140 mm) front to back and 2.75in (70mm) high; it is fitted adjacent to the Telephone, Intercom, No. 4/1 at the main station.

The unit is contained in a Mounting D 92155 using a cover (Part 1/DCO/672, Grey), and a face plate (Part 1/DPL/2136). The 'EXCHANGE LINE' lenses are Caps, Lamp, No. 79C, Red and the 'EXTENSION' lens is a Cap, Lamp, No. 79C, White. The lamps used are Lamps No. 2-45V. The lamps and lenses are easily replaceable but other components are soldered in and should not normally be changed in subscribers' premises.

The cord associated with the unit is a Cord, Inst, No. 18/04AJ, Grey, 72ins (1.8m) and this is terminated with the cabling onto a Block, Terminal, No. 37..., both must be ordered separately.

Diagram Q 535 shows the wiring details of the unit and Q 1015 explains the facilities of the unit.

The unit is available in grey only.

22 CONTROL-UNIT Q 537
The Control-unit Q 537 is a desk unit measuring approximately 6.75in (170mm) wide x 5.5in (140mm) front to back and 3in (75mm) high; it is fitted adjacent to the Telephone, Intercom, No. 4/1 at the main station.

The unit is contained in a Mounting D,92199 using a cover (Part 1/DCO/676, Grey) and a face plate (Part 2/DPL/2135). In addition to the parts contained in Control-unit Q 535 (see par 21) the Control-unit Q 537 contains four key circuits which are used to connect non-multiple extensions and private circuits for intercom calls. When used at an installation with 2nd choice main station facilities, the Part 2/DPL/2135 is changed (see C3036).

This unit is issued without a cord and Q 3015 describes the conditions governing which cord should be fitted.. When a Cord, Instrument No. 18/04AJ, Grey, 72ins (1.8m) is fitted, a Block, Terminal, No. 37... must be used to terminate the instrument cord and cable. When a Connector No. 1046A or No. 1052A is fitted, a Box, Connection, No. 6A must be used to terminate the connector and cable.

Diagram Q(L) 537 shows the wiring details of the unit and C3031 explains the facilities of the unit.

Control Unit Q537	Control Unit Q537 Second Choice

23 NON-MULTIPLE EXTENSION TELEPHONE
A Telephone No. 710 is used to terminate the non-multiple extension. The components to be ordered separately and fitted in the telephone are fully described for the HES No. 3 in Diagram Q 420, and for the HES No. 4 in Diagram Q 550.

Telephone No. 710 fitted with buttons appropriate for a Non-Multiple Extension

24 EXTENSION BELLS ETC
Standard magneto bells, d.c. bells and buzzers are used when extension bells etc are required. Diagram Q 419 shows the connections for HES No. 3 and Diagram Q 545 shows the connections for the HES No. 4.

25 ADDITIONAL RECEIVERS
A Receiver, Watch, No. 8T and a Hook, Receiver, AG are used.

26 LABELS
Particulars of dial labels for Telephones, Intercom, No. 3/1 and No.4/1 are given in C3034 and C3036 respectively, and the labels are described in M0010.

When issued, Telephones, Intercom, No. 4/... are fitted with station identification labels (Labels No. 469/1 and 2) and these are described together with Labels No. 469 in C3036.

27 INSTRUMENTS CORDS AND CONNECTORS
There are two instrument cords and two connectors available for use on HES No. 3 and No. 4 equipment.

Cord, Instrument No. 20/03AJ, 72ins (1.8m) is normally fitted to Telephones, Intercom, No. 3/1.

Cord, Instrument No. 25/04AJ, 72ins (1.8m) replaces Cord, Inst, No. 20/03AJ, 72ins (1.8m) when extra conductors are needed.

Both cords have at one end 41ins (115mm) spade-ended conductor tails for Connection to the telephone, and at the other end, have the spade-ended tails formed into two rows of ten. Each row is held in position by strips of flexible plastic, which are moulded over the shanks of the spade terminals. The remaining five conductors of the Cord, Inst, No. 25/04AJ, ..., 72ins (1.8m) are left free. The plastic 'harness' assists in quick and accurate connection of the conductors to the Block, Terminal, No. 37...

Each cord is stocked in three colours: black, grey and ivory, and in two lengths: 72ins (1.8m) and 120ins (3.0m).

The Connector No. 1046A is normally fitted to a Telephone, Intercom,, No. 4/... and may be fitted to a Control-unit Q 537 if required.

The Connector No. 1052A replaces Connector No. 1046A when. extra conductors are needed.

Both connectors have at one end, 41ins (115mm) spade-ended conductor tails for connection to the telephone or control-unit. At the other end, soldered to the conductors, is a Connector No. 203C55A, which is a 55-way socket for connection to the Box, Connections, No. 6A.

Both connectors are stocked in three colours, black, grey and ivory, and in two lengths, 72ins (1.8m) and 120ins (3.0m) Connectors, with 120ins (3.0m) cords are coded Connectors No. 1046B and No. 1052B.

28 CABLE
The cable used for HES No. 3 and No. 4 installation is Cable, Distribution ... (12W, 24w or 41w) /0.5mm. The size and type of cable to be used is given in C3034 for the HES No. 3 and C3036 for the HES No. 4.

29 POWER EQUIPMENT
The HES No. 3 and No. 4 are mains operated installations, and standby batteries are not provided. A Power-unit No. 51A is provided for the HES No. 3 and a Power-unit No. 52A for the HES No. 4.

30 RINGING SUPPLY
The Converter, Ringing, No. 7, which is mounted inside a Power-unit No. 51A or No. 52A is normally provided when a local ringing supply is required for a non-multiple extension or private circuit. Power-unit No. 100A/1 and 100A/2 for use with HES No. 3 and 4 respectively are equipped with Converters Ringing No. 7 and should be provided at installations initially requiring a ringing supply.

Formerly EI Telephones, Stations, Q1016.

Last revised: March 11, 2023