We found this circuit in the old Mullard transistor reference manual from 1960. The circuit is powered by a single battery and the transistors are germanium common at the time.
This circuit is from Motorola documentation on 1976 power devices. SCRs are powered according to...
Assembled with SMD components this spy can be made very small. We found it in an Australian...
We found this circuit in an old documentation. The operational amplifier of the time can be...