| 摘要 |
PURPOSE: An analog trunk circuit is provided to remove inconvenience to exchange a previous trunk circuit into a new trunk circuit, which is appropriate for an environment in a switching system, by making the analog trunk circuit be operated as a multifunctional analog trunk circuit by software control. CONSTITUTION: An analog trunk circuit has a TIP terminal, a RING terminal, an M terminal, and an E terminal which are connected to a central office line. The analog trunk circuit is connected to a switching circuit through a predetermined transformer, a hybrid circuit, and a CODEC(coder-decoder). The analog trunk circuit connected between the terminals and the switching circuit comprises first relay and second relay(RL9A,RL9B), a third relay(RL1A), a ring path(40), a TIP ground detecting circuit(20), a fifth relay(RL25B), a RING ground enable circuit(80), a bridge diode(BD), sixth relay and seventh relay(RL17A,RL17B), a bypass circuit(50), a RING and hose detecting circuit(60), a feeding circuit(70), an eighth relay(RL25A), and a hose signal detecting circuit. The first/the second relays are driven to control a polarity reverse in a direct inward dialing tie line(DID) trunk mode. The third relay is connected between an output side of the first relay and an upper side of a first winding. The third relay is driven to occupy a loop in a loop trunk mode or a ground start trunk mode. The ring path supplies a transmitting path of a ring signal, when the ring signal is led-in from the central office line. The fourth relay driven in the ground start trunk mode is cut off when the loop is occupied by the third relay. The TIP ground detecting circuit detects the grounded TIP terminal in the ground start trunk mode. The fifth relay is driven in the ground start trunk mode. The ring ground enable circuit grounds the RING terminal in the ground start trunk mode. The bridge diode propagates and rectifies a signal transmitted through the ring path. The sixth/the seventh relays are driven to supply a dial pulse in a loop trunk or the ground start trunk mode. The bypass circuit bypasses a direct current(DC) voltage output from the bridge diode in the loop trunk or the ground start trunk mode. The ring and hose detecting circuit detects the ring signal and a hose signal, and detects the hose signal in the DID trunk mode. The feeding circuit supplies predetermined power to the sixth/the seventh relays in the DID trunk mode. The eighth relay grounds the M terminal when the eighth relay is idle, and is driven in an E and M trunk mode to supply the power to the M terminal. The hose signal detecting circuit detects the hose signal in the E and M trunk mode.
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