AC voltage probe (CB8185E)

This circuit for voltages up to about 20 V was found in a 90s Popular Electronics. The LED can be of any type or color.

Telephone dialer extension (CB9299E)
Found in a Hands-On Electronics from the 90s, this circuit produces the dial tones of an old...
Multiple time base (CB7535E)
Found in Radio Electronics from the 90s, this circuit has several outputs with different pulse...
Telephone Call Indicator (CB17398E)
This circuit, found in 2002 documentation, triggers LEDs when a phone call is received. The LEDs...