Found in American documentation from 1968, this circuit has an acute cut-off of the frequency to which it is tuned and which depends on RC. Transistors may be modern equivalents of general use.
This counter was found in the November 19983 issue of Radio Electronics magazine. The power supply...
This circuit allows coupling optical signals to a TTL input with excellent performance. Among the...
This circuit is from the documentation of Radio Shack 1975. It can be mounted with 12 V relays,...