The Buttinski is a robust hand telephone used in automatic exchanges for call-trace and routine-test purposes. Spade-tag terminations allow it to be readily supplied (or customer adapted) for either plug-in or clip connection to appropriate test points in the exchange equipment.

A press button near the earpiece provides ON/OFF control of the transmitter and also serves to loop the line under test prior to use of the dial.

Construction
The handset is moulded in durable, black rubber, and reinforced throughout its handle section by a metal component-mounting frame accommodating the induction coil and capacitor.

The end cavities of the handset contain terminal inserts, resistors, receiver and transmitter insets and the dial. This rests back-to-back with the receiver and is retained to the mounting frame by three screws. The transducers fit securely into moulded recesses in the mouthpiece and earcap to form complete units that push-fit into moulded grooves in the handset. Components are specially finished to withstand tropical conditions and PVC-insulated wiring is used throughout.

Dial
BPO type 17 trigger dial.
Standard numbering on a black-faced stainless-steel fingerplate.
Pulse speed of 10 p/s with a 2:1 break/make ratio.
Dial cover plate carries the instrument wiring diagram.

Transmission Components
Transmitter BPO type 16, replaceable carbon-granule type.
Receiver BPO type 4T, replaceable rocking-armature type.
Induction coil BPO type 29.
Capacitor 0.5pF, BPO type 8005.
Resistors 120 and 82: BPO types 1 and 2 respectively.

Press button
Plunger type with 'make' springset and 'twist-to-lock' action.

Cord
Two PVC insulated copper-tinsel conductors in nylon braid.
Length 48in (1219mm).

Types
N202328 with un-terminated cord exchanges.
N202329 with double-ended plug.
N202329A with 15-way plug.
N202329B with crocodile clips.

Cord Terminations
(a) Double-ended two-way plug for use on pre-2000, 2000 and 4000-type two-motion selectors in Strowger.
(b) 15-way plug for use on automatic-equipment shelves in crossbar exchanges.
(c) Miniature 'crocodile' clips primarily for use on crossbar wiring/plug terminal fields (for fault-finding purposes).

Overall Dimensions and Weight
Length 12 in (305mm)
Width 3.5in (89mm)
Depth 3.5in (89mm)

Weight 1lb. 14oz (0.85kg)

See also Tele No. 280

Last revised: July 23, 2025