Taking an example of a Raytheon operative as uncommon today, the circuit applies to other operational amplifiers. The formulas are given next to the diagram.
This 1967 Raytheon circuit uses an optical coupler of the era and has a range of 800 to 200 Hz....
This interesting digital counter with relays with complementary outputs was found in the Radio...
This circuit uses a diode as a radiation sensor. The operational ones are old because the...