Current to voltage converter (CB7332E)

This circuit is from a Popular Electronics from the 90s. The integrated circuit admits equivalents that must be tested.

Circuit of Tremolo (CB1490E)
We found this circuit in the National Semiconductor Audio Handbook of 1977. The circuit produces...
Absolute Value Amplifier (CB4902E)
We found this circuit in an old American documentation. The operational amplifier is not common...
Off-hook Telephone Indicator (CB5994E)
This circuit was found in a 1980s US publication. It indicates when the phone is off-hook by...