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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General Purpose Meter (CB23574E)
Measuring capacitances and resistance this simple instrument was found in Radio Electronics...
Current Source with the LM143 (CB14270E)
The LM143 integrated circuit is a high voltage operational amplifier from National Semiconductor that is...
Hexadecimal display circuit (CB24921E)
We found this circuit in the November 1985 issue of Radio Electronics magazine. It uses TTL...