Introduced in the early 1960s, the Collins four-channel 212Z-1 remote amplifier’s design was influenced by answers to a questionnaire mailed to a sample of broadcast stations across the country. Its ...

The function of this circuit is to sound a buzzer, or, optionally, actuate a relay, when a certain moisture level is detected between a pair of probes. The circuit has a ‘memory’ in the form of a flip ...