|In 1955 GEC decided to renumber all their telephones and to start with the prefix
TEL. The MT 7202 which was the original part number for the
this phone which was renumbered to the TEL/1Z/MUU.
GEC PORTABLE MAGNETO TELEPHONE
This instrument has been specially designed for field use, as either an extension telephone or linesmanís telephone, and is suitable for use with any normal magneto switchboard. A call is made by turning a generator handle, and incoming calls are signalled by a two-gong bell within the instrument.
The instrument is completely self-contained in a strong case of good-quality black leather, which is provided with an adjustable carrying strap 54 inches long. The components are mounted on an aluminium alloy chassis, to which a detachable cover is held by four captive screws. Removal of this cover gives full access to all apparatus and wiring.
The transmitter and receiver are combined in the familiar moulded handset, in which is
fitted a pressel switch. The highly efficient speech circuit gives maximum volume with excellent frequency response and sidetone suppression. When packed for carrying, the handset is protected from damage by rubber buffers secured to the chassis cover. The handset cord is 48 inches long and is textile braided. The cord conductors are V.l.R. covered, and additional rubber protection is provided at the point of entry into the handset moulding. Textile bindings are not in contact with the conductors, so that moisture absorption cannot cause leakage.
Line terminals are 2 B.A. Military Pattern.
Ringing current is supplied from a small but powerful hand generator. When not required for use, the generator handle may be detached from the instrument and secured under a spring clip attached to the chassis cover.
Two 1.5 volt batteries, Cat. No. BA4932, each fitted with two terminals, are supplied with each instrument and housed within the case for energising the transmitter. The batteries are of the inert type; the addition of clean drinking water renders them active.
Wiring throughout is insulated with V.I.R. of distinguishing colours to enable various parts of the circuit to be readily identified.
The telephone is satisfactory for signalling and speech in noisy surroundings on lines of 1500 ohms series resistance and 5000 ohms leakage resistance. When the telephone is used in quiet surroundings, the permissible series and leakage losses may be greatly increased without sacrificing intelligibility of speech.
The telephone is suitably finished for use in the tropics.
Length: l0.5 inches (26.7cms)
Width: 6.75 inches (l5.9cms)
Depth: 5.75 inches (l3.35cms)
9 lbs (4.08kgs)
Taken from the GEC Catalogue Leaflet No. STL 8
Pictures taken in 1949