Above, constructed with N jacks for the receiver and unknown port, and jack for external DC supply.
Above, a view of the interior from the front. The jack for external DC can be seen at the rear of the original battery compartment.
Above, a view of the interior from the rear. A 100mA Polyswitch was added to the switch board to provide overcurrent protection, mainly for the external supply / battery.
Above, the waveform at the collector of a multivibrator transistor, and the modulated noise into the bridge (loaded). The modulated noise is quite different to that shown in the manual, partly due to the fact this is a single trace captured on a DSO.