|P.O. ENGINEERING DEPT.
Issue 1, 1939
POLICE TELEPHONE AND SIGNAL SYSTEMS
The system provides for a central-battery type P.B.X. switchboard at police headquarters,
specially adapted to provide - in addition to the normal P.B.X. equipment - equipment for
the termination of party-line circuits, each of which serves a group of street call-points
(normally up to three stations per circuit). Provision is made for fitting lamp signals
and/or bells at the call-points. Telephonic communication can thus be quickly established
between police headquarters, public, and police.
2. In the course of development, various types of switchboard have been introduced. The
design of the switchboards is very similar, but the facilities afforded vary. To
facilitate reference, the Instructions relating to each type will be issued in a
separately numbered series as indicated in Table 1.
TABLE 1 - NUMBERING SERIES of RELEVANT E.I.s
||P 0000 - 0099
||5000 - 5099
||P 1000 - 1099
||P 3000 - 3099
||P 4000 - 4099
|PA 150, 150 TD, 150 TD/
||P 1100 - 1199
||P 3100 - 3199
||P 4100 - 4199
|PA 150 MP
||P 1200 - 1299
||P 3200 - 3299
||P 4200 - 4299
||P 1500 - 1 599
||P 3500 - 3599
||P 4500 - 4599
The key diagram for each type of switchboard gives a list of the circuits and diagrams
used with that particular type of switchboard. These diagrams are as shown in Table 2.
|PA 150, 150 TD and 150MP
|PA 150 TD/GW
|PA 150 TD/BM
CHARACTERISTICS OF DIFFERENT SYSTEMS
4. Switchboard, PA 101
This was the first type of switchboard to be introduced; it is now superseded by
Switchboard, PA 150 PD. Discrimination between police and public calls is
provided. Extension of public calls to other extensions, and discrimination of incoming
calling signals on the three call-points on each party-line, are not provided. Two 2-valve
amplifiers are accommodated inside the switchboard, and can be associated with either/or
both operators telephones for answering calls from the public.
5. Call-point equipment
The call-point consists of a kiosk or pillar. The telephone unit includes a
Telephone No. 164 for police use; the public speak into a transmitter fitted
in the centre of a loudspeaker diaphragm; the loud-speaker transmits amplified speech from
the operator at the switchboard to the caller. When required, a flashing signal light is
provided for attracting the attention of police officers.
6. Switchboard, PA 150
This switchboard superseded Switchboard, PA..101, but is now superseded by
Switchboard, PA 150 TD. Single valve amplifiers, accommodated on the top of
the switchboard, are used in association with special cord-circuits to
transmit amplified speech and also provide for extending pubic calls to special
extensions. Discriminating calling signals for the call-points on the party-lines are also
7. Call-point equipment
This is similar to that for Switchboard, PA 101, except that the units are
provided with discriminating calling facilities.
8. Switchboard, PA 150 TB is arranged for through dialling, i.e.
the caller at an extension is able to dial direct through the switchboard to the public
exchange; in all other respects the switchboard is similar to the PA 150. This switchboard
supersedes PA 101 and 150, and is the present standard type.
9. Call-point equipment
This is identical to that for Switchboard, PA 150.
10. Switchboards, PA 150 TB
In certain instances, due to the demand for a switchboard of large P.B.X. capacity in
addition to the normal police system equipment, it has been necessary to design special
types of PA 150 PD switchboards to incorporate the additional P.B.X. equipment. These have
been designated as follows:
Glasgow City Police - Switchboard, PA 150 TD/GW
Birmingham City Police - Switchboard, PA 150 TD/BM
11. Call-point equipment
This is identical in all cases to that for Switchboard, PA 150.
12. Switchboard, PA 150 MP
This is similar in design to Switchboard, PA 150 PD, but is not provided with
amplifier cord-circuits, and there is no discrimination between police and public calls.
This switchboard was designed for, and at present is used only, on the Metropolitan Police
13. Call-point equipment
The call-point consists of a kiosk. The telephone unit includes a Telephone No.
164, and is used by both police and public. When required, a flashing signal light
is provided for calling the attention of police officers.
14. “Switchboard, PA 350“
This is a 65-line C.B. P.B.X. switchboard modified to
accommodate a strip of keys and associated lamps. Each key actuates a flashing signal at
the corresponding street call-point, which returns a signal to flash the associated
switchboard lamp in unison, thus giving an indication that the flashing signal is
functioning correctly. Party line working is not provided on this switchboard, each
call-point being connected to an individual line. The battery and power plant are
contained in a cabinet fitted at the Police Station. This switchboard was designed for,
and at present is used only on, the Metropolitan Police Inner Divisions.
15. Call-point equipment
The call-point consists of a kiosk or pillar. A telephone of hand-microphone type for both
police and public use, and a plug-in power unit for flashing the lamp signal, are fitted.
The equipment is connected as an external extension on the switchboard.