Phone Call Amplifier (CB21271E)

This circuit was found in an old Electronics Now. The transistors are general- purpose and the circuit is powered by an external source.

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Inductance bridge (CB23524E)
This useful inductance bridge was found in a Radio Electronics from September 1963. The...
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Musical Doorbell (CB24397E)
This circuit found in the October 1975 issue of Radio Electronics magazine uses an integrated...