P.A. 350 POLICE SYSTEM

PA350 Police Telephone System

The PA350 Police Telephone System was used in the area covered by the Metropolitan Police in London, UK.

This system, introduced circa 1937, was completely different to that used on the older PA101 and PA150 systems.  It was cost effective and technically simplified.

The system used centralised switchboards that covered a pre-defined area with posts and kiosks strategically placed.

The new post/pillars were designated Post PA No. 2 by the General Post Office (GPO) and rented to the Police.  Kiosks were owned and installed by the Police force and the GPO would supply the telephone equipment.

The Post PA No. 2 post is sunk into the ground and cemented in place to prevent movement.

When a kiosk was used just the telephone, lantern and Relay-Switch would be required.  Click here for a typical Kiosk installation (Drawing PA 364).

In the mid 1950's Police System PA350 was used as the base for a new national standard.  To this end the PA450 system was introduced which used the Post PA No. 3.  This post was similar to the Post P.A. No. 2, but was produced with thinner cast iron sections and had no underground structure, as it was bolted directly to a concrete base.

Switchboards
Two switchboards could be supplied: Switchboards P.A. 350 10+20+5 (50) or Switchboards P.A. 350 20+20+5 (50). Click here for more details.

Post P.A. No. 2
These posts consisted of a Telephone No. 244 and a Relay-switch Combination No. 2.

The post contained in internal light which was operated by a switch in the middle compartment.

The post had a clear lantern on the roof and there was a press button light test switch in the middle compartment.

There were three doors which were used as follows:-

• The upper door contained the telephone and access was available to the Police and Public.

• The middle door opened downwards to provide a writing shelf and provision was made for storing paperwork in this area.  This door was secured by a key lock.

• The lower door swung open and accommodated the Relay-switch, which was fixed to the rear panel.  There was also a lower shelf with a hole, that would accept a Police cape which was fitted in an inverted "dunces hat" shaped tube.  A first Aid box could also be stored on this shelf.  This door was secured by a key lock.
  In the lower part of the post was a mains intake and fuse box.

Relay-Switch, Combination, No. 2
The lamp was controlled by a Relay-Switch, Combination No. 2 which included the following components:-
18" Cord, Flex., E.L., 250V., Class D3, 0·001 sq. in.
1 x Relay-switch No. 3401NL 1-15 (modified: Tube, Mercury arranged for M type contact action).
4 x Fuses No. 1/1·5.
2 x Fuse-Mounting No. 101A.
1 x Relay-switch. No. 3502NL 1-15.
1 x Plug for Socket-outlets No.8.
1 x Resistor, Coil, No. 12, 10 ohms.
1 x Rectifier-element No. 4/6AA.
2 x Resistor, Coil No. 12, 15 ohms.

Drawing - 63209.
Diagrams - PA 351 / 352.

Telephone
Telephone No. 196CB minus Cord.
Bellset No. 1 or 25.
Wiring diagram - PA 304.

In a Kiosk a Unit, Telephone P.A. No. 3 with a Unit, Telephone P.A. No. 7 were installed.
Wiring diagram - PA 305.

Door Closer
Door-closing, No. 7 used on the telephone compartment door.

PA 350 diagram list

Last revised: February 04, 2023