C MARKETING INSTALLATION
Issue 1, Jan 1971
SECTION, SWITCH, BRANCH EXCHANGE,
COMMON BATTERY, MULTIPLE, No. 9
This Instruction describes the details of, and facilities afforded by, the type of
switchboard known as "Section, Switch, BE, CB Multiple No. 9". This is a
floor-pattern, double-cord board of the multiple type and was installed when more than two
positions were required. The circuit arrangements provided enabled this switchboard to be
utilised in either CB manual or automatic areas.
CB No. 9 PBX in Caxton house - Picture dated 1929
EQUIPMENT AND WIRING (per Section):-
|Exchange line indicators
|Extension line indicators
CAPACITY (per Section):-
Exchange line indicators - 2 strips of 10
Extension line indicators - 10 strips of 20
Exchange line jacks - 8 strips of 10
Extension line jacks - 20 strips of 10 or 20
Cord circuits - 17
CAPACITY (complete Switchboard):-
Exchange lines (bothway) - 160
Extensions - 800
(per Section, without multiple or indicators) 350 lb.
Width (including key-shelf)
Wiring diagram - all circuits LD42
Cord circuit - N1094
Cord circuit divided - N1097
Cord test - N961
Exchange line - N942
Keysender No. 5 - N1094
Extensions - N943
Extensions auxiliary equipment for long lines - N986
Operator's telephone - N947
Night alarm - N946
Ringing circuit - N946
Private wire, explanatory - N949
Private wire short, wiring details - N948 (sheet 1)
Private wire long, wiring details - N948 (sheet 2)
Inter-switchboard private wire explanatory - N949
Inter-switchboard short, wiring details - N948 (sheet 1)
Inter-switchboard long, wiring details - N948 (sheet 2)
Inter-switchboard extension - N981 (Fig 6)
Face equipment - typical 3-Position switchboard - EC1305
Face equipment - typical 7-Position switchboard - EC1306
Typical Relay Rack - EC1117
Cabling Scheme - 3 Positions - EC1121
Cabling Scheme - 7 Positions - EC1119
Construction for Cable Racks - EC1122
MDF 0/240 - method of fitting and cross-connecting apparatus on frame - EC1231
POWER SUPPLY DATA
Minimum permissible PD - 16v
Current per exchange connection at 16v - 0.073A
Current per local connection at 16v - 0.076A
Current per operator's transmitter circuit at 16v - 0.070A
Hypothetical current per Section at 16v - 0.52A
Hypothetical consumption per day per Section at 16v - 3.8Ah
The maximum permissible line-resistance for exchange plus extension lines is specified in
The Sections are of the two-panel type, designed for lining up to form a continuous
switchboard, with the exchange lines and extensions multipled every four panels. The
multiple jacks also serve as answering jacks, the allocation of the indicators is
therefore governed by the position of the corresponding multiple jacks. The ends of a line
of Sections are completed by end-panels, or by cable-turning sections if the number of
cables to be provided is too large to be accommodated in an end-panel. Typical
arrangements of jacks and indicators are shown in Diagrams EC1305 and EC1306.
The exchange lines are terminated on self-restoring drop indicators and the extensions
on doll's-eye indicators. Double cord circuits are provided, each pair being equipped with
a SPEAK and RING key, a RING BACK and DIAL key and two supervisory indicators. The
supervisory signals are disc indicators and, together with the keys, are fitted in the
CB No. 9 PBX - Picture dated 1926
To enable cord circuits to be used for night connections, keys are provided to disconnect
the battery feeds from the tip and ring, and the relay from the sleeve, of each
cord-circuit concerned. Direct connection can then be made between any exchange line and
A breastplate transmitter and headgear receiver is the standard operating telephone for
this type of switchboard; it is terminated on a four-way plug, which is inserted into an
instrument jack (fitted in the keyboard) when the Position is staffed.
During the period when the switchboards are not fully staffed, an operator is enabled by
the operation of the position-coupling key to deal with calls on the adjacent position.
Facilities for ringing, either by hand generator or from power ringing leads, are included
in the equipment of the Sections, Diagram N946 refers.
In manual areas, a "Part No. 1/11555" is fitted on the RING BACK and DIAL
key, to prevent movement to the DIAL position.
A jack in a single mounting is fitted in the left-hand wood stile of each Section, and
wired in accordance with N961.
One night-alarm circuit common to the whole suite of Sections is provided,
Diagram N946 refers.
These are of the negative type, discs being displayed while a call is in progress, and
automatically restored on the termination of the call. Double clears are given on exchange
connections, while on local calls individual supervision is provided.
KEYSENDER No. 5
Now obsolete - but shown to the right.
An incoming exchange call is answered by the operator inserting an answering plug into the
jack of the calling line; this restores the calling indicator and operates the answering
cord-circuit supervisory signal. The SPEAK key is operated and the demand ascertained. Connection to the required extension, if found disengaged after test, is
made by inserting the calling plug into the appropriate jack and operating the RING key. The calling-cord supervisory signal operates when the extension subscriber answers and the
RING key is in the normal position (the calling supervisory signal is inoperative while
the RING key is operated).
OUTGOING EXCHANGE CALL
These are made by inserting a calling plug into a disengaged exchange-line jack, and
- where the main exchange is manual, waiting for the main exchange operator
- where the main exchange is automatic, after the receipt of dialling tone, operating
the DIAL key and dialling the required number. The DIAL key is then restored and the call
proceeds in the normal manner.
PROHIBITION OF EXCHANGE SERVICE ON PRIVATE WIRES
If a private wire is extended to an exchange line, the private wire is disconnected by the
prohibition apparatus, Diagram N949 refers.
Before a plug is inserted into the jack of either an exchange line or an extension, the
operator first tests the line by operating a SPEAK key and placing the tip of the
associated calling plug against the bush of the jack; a click will be received in the
operator's receiver if the circuit is busy.
(From EI Telephones, PBXS, B1020)