This Hughes circuit is from 1968. Equivalent modern components can be used. The input impedance is 1000 M ohm.
Found in American documentation from the 90s, this circuit triggers a buzzer with a Sonalert-type...
Found in an EDN from the 90s, this circuit uses operational amplifiers from that time, which are...
This circuit uses a 4 ½-digit indicator of the type TIL33oA (1 unit) and TIL321A (4 units). Driver...