In use telephone indicator (CB8657E)

Found in a 90s Popular Electronics, this circuit keeps an LED on when a phone is in use. Can be used with extensions.

Reversible Ring Counter (CB6598E)
This circuit was found in a 1966 General Electric documentation. The circuit makes use of PUTs...
Constant Load for Monostable (CB17232E)
This circuit is a variation of the previous one (CIR10372) with a feature that allows the constant...
Double limit test (CB9593E)
This precision circuit can be implemented with other operational ones. We found it in a...