We found this circuit in a 1969 Mullard documentation. The same configuration appears elsewhere in this section. The control range is -2 dB to 19.5 dB at 30 Hz.
The transducer of this circuit is a small ceramic capsule or crystal earpiece and the frequency given...
This circuit for old flashes with xenon lamps was found in a Radio Electronics magazine from June...
This is one of the many hysteresis comparator circuits the reader may find in this section and on this...