| 摘要 |
<p>PURPOSE:To simplify the booster power supply connection control, by detecting a service current supplied to a telephone set, and operating the switch for connecting the booster power supply in case when said current value is smaller than the normal value. CONSTITUTION:The circuits from telephone sets S1-Sn are concentrated by the space division type line concentration stage channel network SDNW, attain to the line circuit trunks LCT1-LCTm, also the switching connection among the LCT1- LCTn is executed by the switching stage channel network NW, and switching is executed among the telephone sets S1-Sn. The telephone sets receive a service current, a calling current, etc. from the LCT1-LCTm. When the telephone set S is in an off-hook state, the service current flows through the route of the current supply circuit PF1, the diode D1, the telephone set S, the current supply circuit PF0, the resistor r1, the supply electric source -VG, and its existence is detected by the detection circuit DET0. Also, whether magnitude of the service current satisfies the normal value or not is detected by the detection circuit DET1. If it is detected by the circuit DET1 that the service current does not reach the normal value, the switch SW conducts, it is connected by the booster power supply +VB, and the service current to the telephone set S is increased.</p> |
