| 摘要 |
An arrangement for establishing an alternative telecommunications path between two telephone subscribers via a telephone exchange in the event of inaccessibility via the ordinary telephone line. A sensor circuit on the premises of at least one of the subscribers is adapted to monitor the telephone line between the exchange and the subscriber in order to detect one or more of the followi ng parameters: voltage drop on the line without simultaenous line current; voltage failure on the line caused by line disruption; absence of dialling tone on the line; DTMF tones on the line; unidentifiable DTMF tones of the line; FSK signals on the line; ASK signals on the line; and pulse signals on the line. A selector circuit is connected to the sensor circuit to connect the telephone subscriber's telecommunications equipment from the telephone line to the alternative telecommunications path upon the presence of at least one of said parameters. The alternative telecommuications path is selected from the group consisting of: another monitorable physical telephone line; a telecom connection via the mains; a radio connection, e.g., GSM, NMT, VHF, UHF; an optical cable connection; an optical, non-physical connection; radio communication via satellite; and an ultrasonic communication connection.
|
