Data transmission system between telephone subscriber location and telephone exchange location during idle telephone condition

摘要

An electrical data transmission system employs a telephone line to transmit data from a subscriber data equipment to a telephone exchange data equipment when the telephone line is idle. A first idle line sensing means is associated with the subscriber equipment and is operable to connect the line to the subscriber equipment when the line is idle and to disconnect the line from the subscriber equipment when the line is busy. A second idle line sensing means is associated with the exchange data equipment and is operable to connect the line to the exchange equipment when the line is idle and to disconnect the line from the exchange equipment when the line is busy.