This sensitive circuit was found in the June 1995 Electronics Now magazine. R1 can be from 10k to 1M depending on the desired sensitivity. Power is supplied by the relay.
This voltage inverter was found in a 1960's Mullard manual. The transistors are from that time. No...
This circuit was obtained from American documentation from the 1980s. Transistors support modern...
This circuit is a wireless temperature transmitter for RF signals in the range of 0.2 to 2 MHz...