Voltage Monitor MC34064 (CB14536E)

The component used in this circuit is uncommon today. The circuit is from Motorola's 1990 Linear Databook.

Acoustic Remote Control (CB17667E)
In fact, this is the circuit also known as “vox”, that is, a relay triggered by sound. This...
Voltage Controlled Low Pass Filter (CB25151E)
Based on an LM36000 OTA this circuit was found in the July 1988 issue of Radio Electronics...
555 with direct relay drive (CB25499E)
Relays up to 100 mA can be driven by the 555 with the recommended circuit. The circuit is from an...