| 摘要 |
PURPOSE:To test a telephone call only by a transmission line, by providing the contact of a changeover relay in a four-wire repeating trunk, and automatically separating a switchboard from the transmission line. CONSTITUTION:When there is incoming from an opposite station, a relay R for incoming discrimination is energized to form a loop between line-side equipped terminals A0 and B0, and thus an originating register OR is acquired to relay a return number from the opposite station to the OR. A marker MKR receives the return number and a line-side equipment position from the OR and, when discriminating return connection, marks the relay F1 of a four-wire repeating trunk ODT. The relay F1 supplies the equipment position of a main switch for return connection indication provided to the ODT to the MKR. On the basis of the equipment position and line-side equipment position, the MKR connects the terminals A0 amd B0 to terminals A2 and B2 through an SW. Then, the relay A1 of the ODT and a return connection relay CH operate to make return connection in the ODT. |
