Differential relay (CB8839E)

Found in a 1969’s Electronic Design, this circuit operates in a narrow range of voltages. Transistors can be replaced with modern equivalents.

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Active Inductor (CB5342E)
This circuit is from an 80's electronic component manual. It has the way to simulate an inductor...
Receiver for Heart Rate Monitor (CB25407E)
This is the receiver for the previous circuit found in the November 1991 Radio Electronics...
Frequency switch (CB8095E)
This circuit was found in a Popular Electronics documentation from the 90s. It is possible to switch...