This circuit is for traditional old-style telephone lines found in an American 1980s documentation. Components are common and the optical coupler can be replaced with an equivalent.
Flybacks are no longer misused. However, if the reader wants to recover an old analog television...
Two alternating are produced by this circuit. The output signal must be applied to a power stage...
This circuit generates sine low-frequency signals. The frequency depends on the twin-T network....