| 摘要 |
PURPOSE:To achieve registraction while reducing a load on hardware by providing a control circuit which holds the transmission line at a dial level for a certain time and detecting the level of a transmission line to discriminate the kind of a telephone set. CONSTITUTION:In an exchange EX, the reception lines RH and RG of a terminal are held at a calling level by applying a bias from a terminal RC to a transistor (TR) 9. Therefore, in a terminal T11, a control circuit CS composed of a time constant circuit TC turns on a TR4 for a certain time to supply the output power VE of a Zener diode ZD2 to an encoder for the prescribed time. Consequently, transmission lines TH and TG are held at a dial level. In the exchange EX, when the levels of the lines TH and TG are detected, a TR6 turns on and the output of a terminal TD has the same potential with a terminal TE for the prescribed time, so the terminal T11 is judged to be a telephone type in this case, thereby achieving equipment registration. |
