P 3003
Issue 2, 1934


1. General
This Instruction details the apparatus items, under their Rate Book descriptions together with general information regarding their provision.


2. “Switchboards P.A.101’
Suitable accommodation will be provided by the Police Authorities, and the following switchboard dimensions are given to assist in the selection.

10-line 20-line 30-line
(a) Height of switchboard 6’ 0” 6’ 0” 6’ 0”
(b) Width of switchboard 3’ 0” 5’ 1” 6’ 6”
(c) Depth of switchboard (maximum) 3’ 0”  3’ 0” 3’ 0”
(d) Depth of switchboard (minimum) 2’ 0” 2’ 0” 2’ 0”

3. The reduction of width from (c) viz. 3 ft. to (d) viz. 2 ft. is possible by dropping the keyshelf, which is hinged for this purpose.

4. “Clocks No. 37’

A mechanical 8-day clock, with 6-inch dial flush-mounted, is provided on the front of each switchboard.

The grouping of switchboard units, in the panels of the switchboard, will be arranged to meet local requirements.

The relay controlling the trickle-charging of the filament batteries will be fitted in a suitable position inside the switchboard.

7. “Unit, Switchboard P.A. No. 1”

This is a “jack-in” line unit for the party-lines, and will be requisitioned on the basis of one per party-line group fitted, plus one spare unit per switchboard - to be held in a position provided inside the switchboard.

8. “Handles, Key, No. 1, Yellow” will be requisitioned and fitted, in place of the black key handles supplied with the unit, on each key associated with a call point equipped with a signal lamp, in schemes where signal lamps are not fitted at every call point.

9. The labels on the units will be forwarded together with engraving schedules, in accordance with the normal procedure, to be engraved with the code for each call point as agreed upon locally.

Additional Units will be requisitioned and fitted as, and when, additional groups of street call points are required.

11. “Units, Switchboard P.A. No. 1 dummy”

These are dummy panels required to fill up the unequipped positions in the switchboard panels containing the party-line units.  The number requisitioned for each switchboard will be the difference between the number of party-line groups fitted and the capacity of the switchboard.

12. “Vibrator, Ringing No. 4A”

These are supplied in accordance with the capacity of the switchboard, and are provided 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 vibrator should be fitted in a position outside the switchroom.

14. “Dynamotor No. 20” is a D.C. to D.C. converter, for providing the high-tension supply to the amplifying valves.  Input 22 volts; output 180 volts, 60 milliamps. One “Dynamotor No. 20 “is provided as part of each switchboard equipment.

“Unit, Amplifying, No. 10” is a two-valve amplifier, two of which are supplied as part of each switchboard equipment, to provide amplified speech currents for the loudspeakers at the street call points.

16. “Valves, Thermionic, No. 76 and No. 77”

One of each is supplied with each “Unit Amplifying No. 10.” No. 76 is a Mullard P.M.6D., and No. 77 is an Osram P.625A.

17. Extension of Public Call Alarm

The relay, with the mercury tube contact, required for this circuit is contained in a wood case, and is supplied with the switchboard.  Where this circuit is required, the relay will be fitted in any desired position within the curtilage of the Police station, and the signal light - consisting of a red-coloured 25-watt electric lamp, obtained locally - will be fitted alongside, in series with the mercury tube contact and electric light mains.  The connexion to the electric light mains for this lamp will be provided by the Post Office with the agreement of the Renter, who will supply the current.


18. “Unit, Telephone P.A. No. 1” is a telephone unit required for a street call point fitted as a “terminal” station, and includes “Hook, Receiver U,” and “Telephone No. 164 with cord instrument No. 380.”  One unit will be requisitioned for each party-line group.

19. Internal signal lamp

When the “Unit, Telephone P.A. No. 1” is fitted in a kiosk, one “Lamp, General Purpose 25-watt” will be requisitioned separately for each unit, for the signal light associated with the unit.

Unit, Telephone P.A. No. 2 is the telephone unit required for a street call point fitted as a side station, i.e., an “A,” or “B“ call point, and includes “Hook, Receiver U” and “Telephone No. 164 with cord instrument No. 380.”

21. Internal Signal Lamp

When “Unit, Telephone P.A. No. 2” is fitted in a kiosk, one “Lamp, General Purpose 25-watt” will be requisitioned separately for each unit, for the signal light associated with the unit.

22. “Hook, Receiver U,” also “Telephone No. 164 with cord instrument No. 380” for use with “Unit, Telephone P.A. No. 1 or No. 2,” can be obtained separately upon requisition, if required.

“Cord instrument No. 380” is 18 inches in length.  This is of the cab tyre flex type, and forms part of “Telephone No. 164 with cord instrument No. 380.” This can be obtained separately upon requisition, if required.

“Cord instrument No. 381“ is similar to ”Cord, instrument No. 380.”  This can be obtained in continuous length, upon requisition, when a long cord is required.

25. “Bracket P.A. No. 1” is a bracket to support the mounting for “Units, Telephone P.A. Nos. 1 or 2” in cases where line units are fitted in a kiosk. It includes the public call door and grille structure, complete.  This is supplied as part of the street pillar, but must be requisitioned separately when the telephone unit is fitted in a kiosk.

“Mounting for Unit, Telephone P.A. No. 1,” is the mounting base on which the telephone units are fitted in both kiosks and pillars.

27. Level of mounting
It is essential for the satisfactory working of the mercury contacts in the telephone unit that the mounting be level, and provision is made for slight adjustment of the level by means of washers.

28. Earthing of Unit and Structure

Since power from the mains is carried into the telephone unit for the working of the signal light, it is necessary that the cover of the telephone unit should be earthed.  The tubing carrying the power cables from the Power Company’s cut-outs to the telephone unit will be earthed in accordance with normal practice, and this tubing will be effectively screwed to the mounting base, at the point where the power cables enter, by means of lock nuts.

29. “Posts, P.A. No. 1”

This is a cast-iron street pillar to accommodate “Units, Telephone P.A. Nos. 1 or 2,” together with “Lantern P.A. No. 1“ where required (for lamp see picture at bottom of page).

This item includes the public call door and grille structure complete, also “Mounting for Unit, Telephone P.A. No. 1,” and a “Lantern P.A. No. 1 dummy.”

A First Aid Compartment is provided in the body of the pillar for the accommodation of a first aid outfit, which, if required, will be provided and maintained by the Police Authority.

One “Key, Lock N “is provided with each pillar for the lock on the door of the police compartment.  Where a number of keys is required by the Police Authority, arrangements should be made to supply these under direct sale terms.  The direct cost of “Keys, Lock N “is 10d. each, and the sale should be negotiated in accordance with Engineering Regulation F. 1/85.

33. Erection

The pillar will be erected, if possible, in the footway alongside the kerb, and will be so placed that the police side, and public side, and also the first aid compartment, will be towards the footway.

The base of the pillar will be sunk in the ground, and suitably set in concrete.

35. Earth plates

An efficient earth is essential at each street call point, and arrangements will be made to sink an earth plate during the erection of all pillars and kiosks.

36. Lead-in pipes

Two pipes G.I. 3/8 inch will be laid through the concrete into the base of the pillar during erection, for the lead-in of the telephone and power cables.

37. Lead-in cable

All cables to pillars will be led-in direct from underground, and, where it is not possible or economical to connect with underground mains direct, the overhead line will be terminated on a pole, or building, suitably situated, and led in by means of underground cable from that point.

The call point numbers will be painted on the grille structure of the public call door, at the left of the grille; and, if desired, on the inside of the police compartment door.  If the call point numbers are engraved on the labels on the switchboard units, the quick identification of a call point from which a call is being received will be facilitated.

“Label No. 206” is a “not in use” label, which is fitted to the public call door of street call points during installation, and is recovered when the system is brought into use.  This is fixed from the inside by means of a bolt, which passes through the grille structure and prevents the public call door from being opened.

“Label No. 201” is a public instruction label, to be affixed to the outside of the public call door on both pillars and kiosks.  It is enamelled iron, with white lettering on a red ground, and reads:

To call, Pull and Hold Door Open
For Public Use

41. If a Police Authority desires any alteration in the above, the matter should be referred to the Engineer-in-Chief (Telephone Section) with full details.

42. Painting
”Red” is the standard colour of paint to be used for all pillars.  After erection, the pillars, which will be issued with a primer coat, will be given one coat of “Paint, Kiosk, Undercoat,” and one coat of “Paint, Kiosk, Finishing, Special Red,” to be obtained upon requisition from the Stores Department.

43. Kiosks
These will be provided by the Renter in all cases (see P.3002) but particulars of the dimensions of, and method of fixing, the public door and grille structure will be supplied to the Renter, so that suitable fixing facilities may be provided for these items.  These details will be obtained from diagram P.A.125.

44. Tools
”Tool, Instrument No. 243” is supplied upon requisition from the Stores Department for operating the triangular-headed screws on “Posts, P.A. No. 1 “ and “Lanterns P.A. No. 1.”

45. “Tool instrument No. 245” is a two-pin driver for locking the fixing bolts of “Label No. 201.”

46. “Lantern P.A. No. 1” is a cast-iron lantern which may 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.

47. Special bracket for kiosks
The lantern is provided with a flat base; when it is required to be fitted on a kiosk, it will be necessary for the Renter to provide, on the kiosk, a suitable bracket to which the lantern may be fitted.  Fixing is effected by means of three bolts and nuts, supplied with the lantern, and the Sectional Engineer will provide the Renter with a copy of diagram P.A. 126 - which is a dimensioned sketch of the drilling required for the fixing of the lantern - so that the bracket may be drilled to suit.

48. Wall brackets

When 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.  The lantern, and electric bulb, will be supplied and maintained by the Department, except in any special case where the position of the lantern on a bracket will present exceptional maintenance difficulty, when the lantern and electric bulb will also be supplied and maintained by by the Renter.

49. “Glass No. 40“

This is a specially-constructed cylindrical lens, and one is supplied with each lantern.  The lens is specially treated to give an amber-coloured light, which is the standard colour for the signal light.

50. Electric bulb
A 100-watt drawn-wire filament electric lamp will be used for the signal light in the lantern, and will be obtained by local purchase.

“Lantern, P.A. No. 1 dummy” will be recovered in all cases when a lantern is provided on a pillar.

52. “Bell No. 60A Unmounted”

The dome of the “Lantern P.A. No. 1” is made of bell metal, and a “Bell No. 60A Unmounted” may be fitted inside this when an intermittent audible signal is required in conjunction with the flashing signal light.  The bell is a solenoid gong movement, and is arranged to provide for working on 100 - 130 volt D.C.; 200 - 260 volt D.C.; or 200 - 260 volt AC. This item will be requisitioned separately when required.

Power Supply for lamp
This will be provided, together with the necessary cut-outs, by the Renter, see P.3002.

54. External wiring of Call Points

In order that the full line-testing facility may be obtained throughout the line, the routing of the line must be from the Switchboard, direct to the “A” call point; thence direct to the “B” call point; thence to the terminal call point; i.e., the external line must be led in and out at the “A” and “B” call points.  It must also be borne in mind that the total line resistance must not exceed 500 ohms.


55. Accommodation for the necessary power plant will be provided by the Renter, see P.3002.

56. Installation
This will be carried out in accordance with the instructions contained in Technical Instructions XXIV, part 1.

57. Main Battery
”Cells, Secondary, Stationary No. 6” will be installed for the four main batteries, where a 30-line switchboard is provided, and “Cells, Secondary, Stationary No. 5” will be installed where 10-line or 20-line switchboards are provided.

58. Amplifier Filament Battery
”Cells, Secondary, Stationary No. 1” will be provided in all cases.

59. Charging Panel
A “Panel, Charging No. 28” will be required. This will be issued without the Ampere hour Meter, which will be requisitioned separately.

60. A “Meter, Ampere hour No. 1/50A” will be required in cases where “Cells, Secondary, Stationary No. 5” are installed; in other cases, a “Meter, Ampere hour No. 1/100A” will be necessary.

61. Charging Plant
This will be in accordance with T.I. XXIV, Part 1, having regard to the power supply available, and the local requirements.

62. Separation of telephone and power Cables
In this system amplified speech currents are employed on certain connexions, and the possibility of interference from induction in the circuits is therefore increased. In this connexion special attention is drawn to the instruction in T.I. XXIV, Part 1, paragraph 100, with special reference to the cabling between the charging panel and the batteries.

63. Power Supply
The power supply and the power cut-outs will be provided by the Renter, see P.3002.

Additional Pictures

Lantern P.A. No. 1


BACK Home page BT/GPO Telephones Search the Site Glossary of Telecom Terminology Quick Find All Telephone Systems

Last revised: September 04, 2019