This is the 1968 MR480 commercial cassette recorder circuit. The circuit was fully transistorized and powered by 4 large batteries. We found the diagram in a Japanese documentation of the time.
This sensitive photo-diode circuit with output compatible with TTL logic was found in a 1972 RCA...
This circuit can send signals in both the VHF and FMN bands with a range of a few tens of meters. The...
This circuit was found in a Popular Electronics from the 80s. It is possible to control a relay...