SIGNAL MONITORING AND AUTOMATIC LINE CUT-OFF APPARATUS ON A TELEPHONE LINE

摘要

In a communication system in which both voice signal generating devices such as telephone and data signal generating devices such as fax and modems share and are coupled to the same telephone lines, a monitoring and indicating apparatus is provided which determines whether the line is being used and what type of device is being used thereby to prevent other terminal devices accidentally from disturbing the ongoing communication. The apparatus comprises a data signal detector for detecting a data signal along the telephone line, a voice signal detector connected to the telephone lines in parallel with the data signal detector for detecting whether the telephone line is in use, a display and indicator including a voice signal indicator connected to the voice signal detector which is activated along when the telephone line is being used and a data signal indicator connected to the data signal detector which is activated when the telephone line is being used for data communication, and a cut-off device which is located in between the telephone line and the additional communication device which opens to prevent the telephone from disturbing the data communication when both the voice signal detector and the data signal detector indicate that the line is used for data communication.