P.O. ENGINEERING DEPT.
Issue 3, 1957
POLICE TELEPHONE AND SIGNAL
(USING "SWITCHBOARDS, P.A. 150MP")
Installation Details—Department's Responsibilities
This Instruction gives details of the provision and installation of the Dept.'s
plant. A list of diagrams relating to this system is contained in P 1207.
(EXCEPT POWER PLANT)
2. "Switchboards P.A. 159 MP"
The Police Authorities will provide suitable accommodation for the
switchboard, the dimensions and weight of which are given below:-
|Height of switchboard
|Width of switchboard
|Depth of switchboard (max)
|Depth of switchboard (min)
3. The . reduction of depth from 3ft. to 2 ft., is possible by securing the
keyshelf in a temporary. vertical position, to facilitate handling and placing.
the switchboard in position.
4 Additional equipment
Equipment required for circuits in excess of the, equipped capacity of the
switchboard should be obtained on requisition in the normal manner.
The equipment is included in the Rate Book, under the title of Kits, P.A.
5. "'Clocks No. 43"
A mechanical. 8-day clock, with 5-inch dial, is provided with the switchboard.
6. "Units, Switchboard, P.A. No. 3
This is a "jack-in" line unit for the termination of a party-line and should be
requisitioned on the basis of one per party-line group fitted, plus one spare
unit. per switchboard to be held in the position provided inside the
switchboard. Additional units should be requisitioned and fitted as and
when additional groups of Street call-points are required.
7. The grouping of switchboard units in the panels of the switchboard should
be arranged to meet local requirements.
8. "Caps, Lamp"
These are provided for the switchboard units, and should be fitted as follows:-
Fault - White with black ring
"A" Call - White
"B" Call - White
"Terminal" Call - White
9. "Handles, Key, No. 1, Yellow"
These should be requisitioned and fitted in place of the black key hand1es
supplied with the unit, on each key associated with a call point equipped with a
signal lamp, if signal lamps are not at each call point.
The labels on the units should be forwarded together with engraving schedules -
in accordance with the normal procedure - to be engraved with the code and
number of each call point as agreed upon locally.
11. "Units, Switchboard P.A. No. 1, Dummy"
These are dummy panels required to fill up the unequipped positions in the
panels containing the party-line units. The number requisitioned for each
switchboard should be the difference between the number of party-line groups
fitted and the capacity of the switchboard.
12. "Vibrators, Ringing, No. 4A"
These are provided in accordance with the capacity of the switchboard and are
supplied with the switchboard. They jack-in on a metal frame for wall
mounting. As the noise during operation is likely to be disturbing to" the
operator, the vibrators should - where possible - be fitted in a position
outside the switchroom.
13. "Dial, Auto, No. 10....." and "Cord, Instrument, No. 5/19E"
These should be requisitioned separately and fitted on P.A. switchboards
installed in an automatic area. For P.A. switchboards fitted in a non automatic
area, a "Dial, Auto, Dummy, No. 2" should be requisitioned.
14. Operator's instrument
Two instruments should be requisitioned for each switchboard, and may be of the
handset type ("Telephone No. 184") or the breast-plate type ("Transmitter No.
23A together with "Receiver, Headgear, No. 10A").
15. "Unit, Telephone, -P.A. No. 7T"
One of these units is required' for each street call-point equipped as a
"terminal" station. A "terminal" unit is required for each party-line,
irrespective of the number of call-points connected. thereto.
16. "Unit,' Telephone, P.A. No. 7A"
One of these units is required for each street call-point fitted as a
side-station on the A-wire of a party-line (i.e. an "A" call-point).
When only two call-points are connected to a party-line, a "Unit; Telephone,
P.A. No. 7A" and a "Unit, Telephone, P.A. No. 7T" should be provided.
17. "Unit, Telephone, P.A. No. 7B"
One of these units is required for each street call-point fitted as a
side-station on the B-wire of a party-line (i.e. a "B" call-point).
18. Sub-station equipment
Only two types of telephone are available, i.e. for "A" and" terminal
call-points. If a sub-station would normal] "B" call-point, a "Unit,
Telephone, No. 8A" should be provided for the sub-station and converted to "B"
point working by fitting the "B" point cam supplied with the unit. This
will also necessitate changing the signalling (P) relay connexion from terminal
1 to terminal 2 (see P 1204).
19. "Unit, Telephone, P.A. No. 8A"
On these units is required for each sub-station fitted as a side-station on the
A-wire or B-wire of a party line (see P 1204). The unit is made up as a
1'-set for wall fixing and includes an alarm bell and a "B" point cam, which is
supplied for converting the unit to "B" point working. Where this
conversion is necessary, arrangements should be made for it to be done locally.
Extension bell terminals are provided in the unit and: an extension bell
(trembler type, continuous or non-continuous) should be provided when required.
A mounting is not required.
20. A "Unit, Telephone, P.A. No. 8T"
These are required for a sub-station fitted as a "terminal" station. This
unit is similar in construction to the " Unit, Telephone, P.A. No. 8A" but does
not include an alarm bell. This should be provided by fitting a "Bell No.
56A and a "Boxes, Battery for 3 dry cells" with two "Cells, Leclanché D.R.2.
21. "Mounting for Unit, Telephone, P.A. No. 3"
This is the mounting base on which the telephone units are fitted in both kiosks
and pillars. One should be requisitioned for each "Unit, Telephone, P.A.
No. 7A, 7B or 7T" fitted either in a street pillar or kiosk.
22. Level of rnounting.
It is essential for the satisfactory working of the mercury contacts in the
telephone unit that the mounting be level.
23. Earthing of power cable sheathing.
In accordance with normal practice, the lead sheathing of the cable carrying
power from the Power Company's cut-outs to the telephone unit should be suitably
24. Earth plates.
An efficient earth is essential at each street call-point, and arrangements
should be made to sink an earth-plate during the erection of all pillars, and
kiosks. For detailed method of earthing, see PROTECTION, General, S 3901.
25. Lead-in pipes
An asbestos-cement pipe for the telephone cables, to be provided by the renter,
should be led into the base of kiosks and pillars during erection. Where
required, a suitable asbestos-cement pipe should also be provided to accommodate
the power cable (see P 3201 Par. 11). To prevent entry of gas, the pipe
should be effectively sealed in accordance with Lines, Underground K3003.
26. Lead-In Cable
All cables to pillers and kiosks should be led-in direct from the underground
and if it is not possible or economical to connect with underground mains
direct, the overhead pipe should be terminated on a pole or building, suitable
situated and led-in by means of underground cable from that point
27. Kiosks and Pillars.
These should be provided by the renter in all cases (see P 3201) but particulars
of the dimensions of the telephone unit and mounting should be supplied to the
renter, so that suitable fixing facilities may be provided for these items.
These details should be obtained from Dgm. PA305, a copy of which should be
supplied by the Area Engr. to the renter. Instructions to the public are
the renter's responsibility.
28. Special bracket for kiosks
The lantern is provided with a flat base; when it .is required to be fitted by
the Dept., it will be necessary for the renter to provide - on the kiosk or
pillar - a suitable bracket to which the lantern may be fitted. Fixing is
effected by three bolts and nuts supplied with the lantern, and the Area Engr.
should provide the renter with a copy of Diagram PA 126 (which is a dimensional
sketch of the drilling required for the fixing Of the lantern) so that the
brackets may be drilled accordingly.
A "Key, Pillar" - supplied upon requisition from the Supplies Dept. - is
required for operating the triangular-headed screws on "Lanterns".
30. "Lantern, P.A. No. 1"
This is a cast-iron lantern which should be fitted on "Post, P.A. No. 1" or in
other positions as required, to provide a visual signal for calling the
attention of police officers. The lantern and lamp are normally supplied
and maintained by the Dept., but the renter may, if he desires, supply and
maintain these items. In London, the lantern and lamp are in all cases
supplied, fitted and maintained by the renter.
31. Wall brackels.
Then it is required to fit the lantern on a wall bracket,. the bracket and
cabling between the telephone unit and the lantern will be supplied, fitted, and
maintained bY the renter. Where the position of the lantern on a bracket
will present exceptional maintenance difficulty the lantern and lamp should be
supplied and maintained by the renter, or where, as in London, the renter
desires to supply and maintain these items. Otherwise the lantern and lamp
will be supplied and maintained by the Post Office.
32. Glass, No. 40".
This is a lens of amber-coloured glass for "Lanterns, P.A. No. 1". One is
supplied with each lantern.
33. Electric lamp.
A "Lamp, Gene, Service 100-watt .. volts" should be used for the signal light in
34. "Lantern, P.A. No. 1 Dummy"
This item should be requisitioned and fitted if a "Lantern, P.A. No. 1" is not
35. "Bell, No. 60A, Unmounted"
The dome of the "Lantern, P.A. No. 1" is made of bell metal, and a "Bell, No.
60A, Unmounted" should he fitted inside this when an intermittent, audible
signal is required in conjunction with the flashing signal light. The bell
is arranged for working on D.C. 100-130 volts or 200-260 volts, or A.C. 200-260
volts, and should he requisitioned separately when required.
36. Lamp Supply.
The power supply for the lamp, together with the necessary cut-out, will be
provided by the renter (see P 3201).
37. External wiring of call-points.
So that the full line-testing facility may be obtained throughout the line, the
routing of the line should be from the switchboard, direct to the "A"
call-point, thence to the "B" call-point, and thence to the "terminal call-point
(i.e. the external line should be led in and out at the "A" and "B" call-points.
Where additional side-stations are provided, continuity must be maintained by
leading in and out at these points also.
38. Line presentation.
To avoid bunching of conductors and to facilitate fault location, the line wires
should be terminated in a "Block, Terminal No. 20/4" at the "A" and "B"
call-points. The terminal block should be fitted immediately below the
39. In exceptional circumstances, the line plant serving the call-point on a
party-line may be teed at the exchange or cross connection cabinet
(TRANSMISSION, Telephones, B 3572). In such cases, the line wires
should be terminated at the "A" and "B" call-points as for a "terminal"
call-point (i.e. the "Block, Terminal No. 20/4" should be omitted). Additional
side-stations should not be provided on a call-point party-line having its line
plant teed at an exchange or cross-connexion cabinet.
40. Line Resistance.
The total line loop resistance between the police switchboard and any call-point
should not exceed 500 ohms and the minimum permissible insulation resistance is
50,000 ohms (TRANSMISSION, Telephone, B 3572).
For the necessary power plant, this should be provided by the renter (see P
42. Installation of cells.
The power plant should be installed in accordance with POWER, Cells, C 3001 and
43. Main batteries.
Four 24-volt batteries are required and the secondary cells and ampere-hour
meters to be used are as detailed:-
Positive Battery - Cells, Secondary, Enclosed, No. 3 - used with Meters,
Ampere-Hour, No. 1/100A.
Negative Battery - Cells, Secondary, Enclosed, No. 4 - used with Meters,
Ampere-Hour, No. 1/100A.
44. "Panel, Charging, No. 28"
This is required. The panels are issued without the ampere-hour meters,
which should be requisitioned separately.
45 Charging Plant.
The charging plant should be in accordance with P 3104, having regard to the
power supply available and the local requirements,
46. Power Supply.
The power supply, including main switch, should be provided by the renter - (see
P 3201) who will make the necessary arrangements with the Supply Authority for
lead-in, meter etc.
for secondary-cell 10
47. Accommodation for Secondary Cell log books and Spare Parts.
A "Cupboard, Tool" should be obtained on request from the Controller of
Supplies, Ministry of Works on Form OW901.