| 摘要 |
PURPOSE:To decrease number of components and to reduce the cost by using a 16Hz call tone detecting section and a polarity detecting section in common in a network control circuit of a telephone exchange line. CONSTITUTION:In performing the detection of a 16Hz ring signal attended with the incoming and the polarity inversion of subscriber lines 1a and 1b, a diode 8 at one end of diode bridges 6-9 used for the detection of the 16Hz ring tone signal is separated from the circuit by operating a relay contact 22 and the subscriber lines 1a and 1b are short-circuited via a resistor R23. Thus, the full wave rectifier function comprising the diodes 6-9 is lost in this way, and the polarity of the subscriber lines 1a and 1b is decided by using the diodes 6, 9, a capacitor 11 and a relay 14. |
