Experimental television receiver

The equipment comprises three units: a sound receiver working on medium waves; a short-wave visual receiver; and a power supply unit, including the deflecting circuits. The visual receiver is a superheterodyne with three i.f. stages, a diode-triode detector-amplifier, and one v.f. amplifier. Its pass-band is more than 1 Mc./sec. The deflecting circuits use the usual condenser charged through a high resistance, but the 4000-V supply is used. Thus a small portion of the curve is straight enough and also gives sufficient amplitude of p.d. The circuits are balanced. The filament of the kathode-ray tube is connected to the filament of a verticaldeflection thyratron, so that, when the latter discharges, a p.d. pulse is applied which suppresses the ray during the return. Provision is made for variable definition, and for operation with or without a separate vertical synchronising signal. Other features are a voltage-doubler circuit for the kathode-ray tube anode supply, and thermic relays for push-button starting. Very stable pictures have been obtained with a field-strength considerably below 1 mV/m.