| 摘要 |
An improved telephone interface device communicatively couples a local telephone set to an inside telephone wire which, in turn, is communicatively coupled to an outside telephone line from a central office of a telephone service provider. The interface device includes an on-hold switch, a ring detector, a tone decoder, and a coupling switch, all of which are coupled to the bridge via an internal signal line and a control computer. The touch tone decoder receives input tone sequences from the bridge, decodes the tone sequence, and outputs a bit signal to the control computer. The on-hold switch is responsive to a command from the control computer, and is operative to maintain the signal line at a first predetermined voltage. The coupling switch communicatively couples the signal line to a node line. When the node line is coupled to the signal line, a user at the local telephone set may communicate with another user in the home, or with an outside user. The detector compares the voltage on the signal line with a plurality of predetermined voltage ranges. If the voltage on the signal line is within a predetermined voltage range, then the comparator outputs a logic high value to the control computer. A local phone connector is communicatively coupled to the local telephone set and to the node line. During intercom operations, DC power is supplied to the local telephone set via an intercom power switch and the local phone connector. |
