| 摘要 |
PURPOSE:To prevent malfunction such as resonance of bells with a simple constitution, by providing relays opened at the application of DC and closed at no call by the number of telephone sets, to a circuit connecting plural telephone sets in parallel with a pair of communication lines. CONSTITUTION:Dial telephone sets 10, 20 are connected in parallel to a pair of communication lines L1, L2 to constitute channels 11, 21, which are provided with relays 22, 12 connecting respectively normally-closed contacts 23, 13. In case of incoming waiting state, the contacts 13, 23 are closed, then an incoming signal to the lines L1, L2 rings both bells of the telephone sets 10, 20. When a handset of the telephone set 10 is hooked up, the channel 11 is conductive in terms of DC, the relay 12 is operated, the contact 13 is opened and the channel 21 is disconnected. In case of outgoing call from the telephone set 10, the contact 16 is intermitted, and a dial pulse is transmitted to the station side, and when the contact 16 is interrupted, a capacitor 27 connected to the bell 26 of the telephone set 20 is charged with a voltage from the station, and when the contact 16 is contacted, the contact 13 is interrupted, no C 27 is discharged and the bell 26 does not ring. |
