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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Twin-T Oscillator Using the 741 (CB249E)
An excellent low frequency sine signal is produced by this oscillator. The frequency is determined by the...
RF Wattmeter (CB4886E)
This watt meter was found in an old telecommunications documentation. The circuit is interspersed...
Pulsing Tone Generator 4011 (CB10743E)
Although it is a common configuration today, these circuits were taken from an old publication. The...