We found this circuit in the 1964 RCA transistors manual. The sensor may be a common LDR and the transistor BC558. The relay has an operating voltage according to the power supply.
For the 7 to 10 MHz band L1 is formed by 3 turns of 22 to 28 AWG wire in a ferrite core 15 to 20...
We found this interesting timer circuit or CMOS timer in a 1988 publication. The circuit is still...
This audio mixer was found in an old American documentation. The potentiometers are 1M and the...