Telephone in use indicator (CB9467E)

We found this circuit in a Hands-On Electroncs from the 90s. The circuit uses an LED indicator. Diodes are general purpose types.

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AD590 or AD592 Temperature Sensor (CB25446E)
This circuit allows you to read temperatures with a common digital voltmeter. We found it in the...
Unit gain MOSFET stage (CB6966E)
Found in American documentation, this amplifier stage has unit gain and a high input impedance. It...
20 A TTL Shield (CB7253E)
This circuit is from an old American publication, using transistors of the time and operating with a 48...