This interesting digital counter with relays with complementary outputs was found in the Radio Electronics magazine of October 1961. The supply voltage is in accordance with the relays used.
The speed indication of this circuit is made on an analog instrument. The circuit is used to count...
This circuit was obtained in a 1967 Raytheon manual. The company's component is an optical coupler with...
We found this circuit in a 1960 Sylvania transistor manual. The relay can be 12 V and C1...