This interesting circuit uses a sodion valve that we have already described in an article on the website. The circuit uses several batteries for power. The phone is of high impedance.
This circuit was found in a 1989 documentation. The circuit directly controls a power load by the use...
This small telephone transmitter uses a telephone capsule as a microphone. The L1 coil has 4 to 5...
This emergency light circuit does not include a battery charger or an intelligent system to...