Proportional temperature controller (CB21277E)

This circuit is from an Electronic Design from the 90's. The main integrated circuit is uncommon nowadays.

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Logic Gate with LED Indicator (CB14628E)
This circuit is from a technical documentation from Texas Instruments from 1978. In it we have the...
Operational Multiplier and Divider (CB13812E)
We found this circuit in a publication with experiments with operational amplifiers from 1973. The...
FM modulator with varicap (CB6913E)
Using a varactor or varicap, this 1969 Electronics World circuit has a modulation range from 75...