| 摘要 |
PURPOSE:To prevent malfunction from being caused when an output voltage of a decoder reaches in error a negative DC maximum level by inactivating only the decoder after the reception of the 1st selection numeral and bringing again the decoder into the operating state after all numerals are received. CONSTITUTION:When an SCN signal comes to a 2W line, a feeding/supervisory circuit SCN detects it so as to activate relays RL1, RL2. A power supply E of the coder COD is applied with closing of a contact rl1, the power supply E of the decoder DEC is applied through the closing of a contact rl2 so as to bring the both into the operating state, a dial tone DT is transmitted to a caller and the system enters the reception state of the 1st selecting numeral. When the reception of the 1st selecting numeral is detected by the circuit SCN, its control circuit CONT restores only the relay RL2, the contact rl2 is opened, the decoder DEC is brought into the inoperating state and when the circuit SCN detects the reception of all figures, the relay RL2 is activated again so as to close the contact rl2 thereby bringing the decoder DEC into the operating state. |
