Marconi TF340 Output Meter



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Manufacturer Marconi
Model TF 340 (Air Ministry Output Meter type 2)
Age 1940's
Service Data No
Condition Fair, working
Comments This meter is used to measure the audio output of receivers or lines. two switches select the impedance of the meter (to match the circuit under test), and a third selects the measurement range. The meter has an Air Ministry plate, describing it as "Output Meter, Type 2", which would indicate the unit has seen service with the RAF.

Internally, the impedance switches select taps on a matching transformer, while the range switch selects the relevant meter shunt. The meter itself, is a moving coil type with a copper oxide rectifier.

I would guess that this is a wartime instrument, as the front panel shows signs of being stamped twice to give the lettering - there is a "ghosting" effect on some of the wording, in normal circumstances, this would not have got past Marconis inspectors!

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Copyright J.Beacon & M.Wroe-Parker 2003 & 2004