DTMF Decoder (CB25048E)

This circuit was found in the 1987 Radio Electronics magazine. The components used are integrated circuits of the time.

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RIAA Preamplifier (CB12172E)
This circuit makes the RIAA equalization of signals obtained from a record player for recovery in other...
Four Transistors Reflex Receiver (CB18301E)
This is a diagram of a 1958 commercial receiver. The circuit was found in documentation at the...
Frequency doubling oscillator (CB9634E)
This circuit uses an 18 MHz crystal to generate 36 MHz signals. We found it in an 80's...