|P.O. ENGINEERING DEPT.
Issue 2, 1957
POLICE TELEPHONE AND SIGNAL
(USING" SWITCHBOARDS, PA 150 AND 150 TD ")
An improved switchboard ("Switchboard PA 150") has been introduced for
the police telephone and signal system. This switchboard possesses
facilities additional to those provided on "Switchboard, PA 101" (see P
1001) which it supersedes.
In "Switchboards, PA 150" the through-dialling facility has not been
provided for. All later supplies of these switchboards will give this
facility, however, the modification being indicated by the title
"Switchboard, PA 150TD ". Where a definite request is made for
through-dialling on existing "Switchboards, PA 150", this can be provided by
means of a "Unit, Auxiliary Apparatus, PA 266". Applications for this
facility should be referred to the Eng. Dept. (Sl).
3. The switchboards provide for the termination of:-
- Public exchange lines, to any type of exchange system.
- Inter-switchboard private wires. These terminations are readily
converted to inter-switchboard extensions when required.
- Internal and external extensions.
- Public call extensions.
- Street call-points, i.e. police kiosks or pillars, on "Units,
Switchboard, PA No. 2".
The facilities provided are as follows:-
- Connexion to the public exchange of any street call-point (police
side), internal or external extension, or inter-switchboard extension
line if required.
- Connexion of street call-points (public side) to special public call
extension (if provided).
- Speaking from street call-point (police side) to other street
call-points (police side) on the same, or any other, party line.
- Signalling and speaking to Street call-points (police side)
(i) separately, or
(ii) simultaneously, in groups of any number.
- Distinctive calling signals, at the switchboard, to indicate whether
a call is from a member of the public or from a police officer, and from
which particular street call-point the call originates.
- Visual indication, by means of a lamp on the switchboard unit, that
the public side of a street call-point has been operated whilst a police
call is in progress at another street call-point on the same party line.
- Visual indication, by means of steady signal lamps which can be
brought into use (either internally and/or externally at a police kiosk,
or externally on a pillar), when desired, during the period that the
public call door is open, thus attracting the attention of police
- Automatic fault indication on all lines terminated on switchboard
units, i.e. street call-point lines, whereby any fault is brought to
notice visually immediately it occurs. Exceptionally, where the line
plant serving a call-point party line is teed at an exchange or
cross-connexion cabinet (see P 3103), automatic fault indication is not
given for a disconnexion between the teeing point and the "A" and "B"
- In order that the apparatus fault-duration period may be reduced to
a minimum, the switchboard units, amplifiers and ringing vibrators are
of the unit type and are jacked-in.
- Through clearing on exchange calls.
- Divided clearing on extension to extension calls.
- Supervision on police calls to police on the same or any other party
- Supervision on extended public calls.
- Through-dialling by extensions on originating calls (see par. 2).