| 摘要 |
PURPOSE:To obtain a test system for channels suitable to time-division switching by equipping a time-division switchboard with a channel testing device having a ring- back tone signal detection circuit and matcher circuit, and a signal returning switching method. CONSTITUTION:Once calling telephone set B is connected to a called telephone set, a ring-back tone RBT signal is sent from highway HW2. Channel controller SPC controls branching and switching circuit D/I to branch this signal to test line TL2. This is let to RBT detection circuit DET, which detects RBT signal and then controls signal return switch SX through channel controller SPC. After passing through time-division channel HSW and decoder DEC, the RBT signal reaches circuit D/I from switch SX by way of coder COD and circuit HSW, and is supplied to test line TL2 before being inputted to matcher circuit DCC. Circuit DCC collates the input of TL1 with that of TL2 and when they agree, unit SPC makes a decision that the channel is formed correctly and then releases switch SX. |
