Off-hook Telephone Indicator (CB5994E)

This circuit was found in a 1980s US publication. It indicates when the phone is off-hook by triggering an indicator.

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2 kHz Alarm (CB4877E)
This simple alarm with integrated CMOS sounds a piezoelectric transducer when the sensor circuit...
0 to 30 V x 3 A Regulator (CB4843E)
In this application we show how to get tuning from 0 V to an LM350 regulator IC. The setting also...
Sequential Timer 555 (CB1263E)
We found this configuration in a Radio Shack documentation from 1977. Here we have the way to...