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 is from a 1982 publication. It is a sequential effect of accelerated and intermittent LEDs....
This PLL with operational amplifiers was found in 1969 documentation. The configuration can be...
Here is a simple source without a transformer for currents up to 50 mA. The voltage depends on the...