P.A. 150MP POLICE SYSTEM

POLICE TELEPHONE AND SIGNAL SYSTEM
(USING SWITCHBOARDS, P.A. 150MP)
Installation Details - Department's Responsibilities

1. General
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.

HEADQUARTERS EQUIPMENT
(EXCEPT POWER PLANT)

2. "Switchboards P.A. 150 MP"
The Police Authorities will provide suitable accommodation for the  switchboard, the dimensions and weight of which are given below:-

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. No.....".

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. Grouping
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.

10. Labels
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 switch-room.

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").
 

CALL-POINT EQUIPMENT

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 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, Leclanche 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 mounting
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 earthed.

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 pillars 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 Diagram 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.

29. Tools
A "Key, Pillar", supplied upon requisition from the Supplies Department, 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 brackets
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 the lantern.

34. "Lantern, P.A. No. 1 Dummy"
This item should be requisitioned and fitted if a "Lantern, P.A. No. 1" is not required.

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 protector.

39. Party Line wiring
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).

POWER EQUIPMENT

41. Accommodation
For the necessary power plant, this should be provided by the renter (see P 3201).

42. Installation of cells
The power plant should be installed in accordance with POWER, Cells, C 3001 and C 3002.

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.

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.

List of diagrams
 

Last revised: December 02, 2022