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 electronic flash circuit was found in the March 1961 Radio Electronics magazine. The circuit...
Like the previous circuit, this is used in the analog part of the telephone lines. The same...
This circuit was found in documentation from the 90s, being indicated for use with tape recorders given...