This small audio amplifier uses germanium transistors and a 12 V supply. The circuit is from a Japanese technical documentation from the 1960s.
This circuit is from 1995 documentation. When the phone is lifted, the relay closes its contacts by...
This astable NAND TTL provides complementary signals. The circuit must be powered with 5 V and...
This photo-relay uses a Darlington stage to increase sensivity. Any photo-transistor can be used....