Circuit arrangement for subscriber telephone sets powered via the subscriber line with electronic control and switching means in telecommunications systems, in particular telephone systems

摘要

The circuit arrangement for subscriber telephone sets powered via the subscriber line with electronic control and switching means in telecommunications systems, in particular telephone systems, essentially comprises a capacitor which is charged initially via the line wires in order then to supply the control current for an electronic switching means which closes the loop. The electronic switching means which closes the loop initially remains blocked with a switching transistor during the charging process. The same charging transistor is also used to block the electronic switching means when the electronic control device can maintain the loop circuit with a low impedance.