| 摘要 |
For single line telephone service, let red/green denote a pair that is connected to the central office, and yellow/black denote an unused pair, but which also appears at the connections to the subscribers equipment. Any computer or other device that is to be interruptible by an ordinary handset is connected to red/green through a phone service re-allocation circuit that is also connected to, and that monitors, yellow/black. An extension allowed to cause an interrupt is connected to yellow/black. For RJ-11 connections an adapter routes the yellow/black (in the wall) over to the terminals normally used for red/green. An off hook condition of the interrupting equipment connected to the adapter now serves as part of a signal to the re-allocation circuit. Upon a signal, the re-allocation circuit terminates the access of the interruptible equipment to the red/green pair, and bridges the red/green pair to the yellow/black pair instead. The signal can range from a simple off hook condition to the further detection of dialing a certain digit or sequence of digits (e.g., 9 or 911), and may involve supplying a false dial tone to the interrupting equipment and the stored re-dialing those digits to prevent an uninformed user from thinking "the line is dead". If the interruptible equipment is on hook, the re-allocation circuit automatically disconnects it from the central office red/green, bridges that red/green to yellow/black, and then monitors the interruptible equipment for off hook.
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