Editorial Consultant: Rod Burman

OSRAM BARRETTER ON GPO BASE, 1930's

Barretters are temperature sensitive resistors used for stabilising voltages in wireless receivers, usually powering the heater circuits, of AC/DC receivers.
Acting like a resistor but with constant current characteristics, a current over a particular range can be held constant over a range of varying voltage. A Barretter usually consists of an Iron wire held in Hydrogen filled glass envelope. Also used for many other applications.

A0694

GPO VT No 4 VALVE, 1920's

GPO VT No 4 Valve, a Triode of the 1930's on an American UV4 pin twist on base.

A0640

GPO VT32, 1925

Early Telephone Triode amplifier of 1925, with BPO twist on base.

A0644

CV257 MOV HOUSEKEEPER SEAL VALVE, 1943

CV257 Triode Valve used in VHF power amplifiers, with the Anode connected by a Housekeeper seal (the copper disc), invented by A.A.A. Housekeeper, who solved the problem of bonding ductile metal to glass.

A0673

GEC TRANSMITTER POST OFFICE TELEPHONES, 1950's

GEC ACPT21 weight 36Kg's 665mm high 2Ft 2inch long hence the two handles for lifting. ACPT= Air Cooled Pentode Transmitter.
Transmitting Valve used by Post Office Telephones.

A0215