Found in a 1967 Ferranti documentation, this circuit uses a LDR from that time as a sensor. Transistors can be replaced with modern equivalents.
This heartbeat sensor circuit was found in the July 1992 issue of Radio Electronics magazine. The...
We found this circuit in the 1982 SGS integrated circuit manual. The integrated circuit is not...
This TTL pulse stretcher or stretcher was found in a 90's EDN. The time constant R x C1 determines...