| 摘要 |
In a security and alarm service environment, a method and system for verifying the continuity of a telephone line 317 connected to a subscriber terminal unit (STU) 310 at a customer's premises. The STU 310 is connected by telephone line 317 to a network interface 315 which is connected to a line unit 320 by a twisted pair 325. Line unit 320 is located in remote terminal 330 which is connected to switch 335 by digital loop 340. Switch 335 is connected to scanner 345 by trunk group 350 and SMDI link 355. A low tone generator in STU 310 generates a low frequency tone that is transmitted to line unit 320. If telephone line 317 is cut, if STU 310 malfunctions, or if an alarm condition at the customer's premises is detected by STU 310, then the low tone is not received by line unit 320. Remote terminal 330 encodes a signaling bit that is transmitted over digital loop 340 to switch 335. The encoded signaling bit indicates whether or not the low tone was received by line unit 320. Switch 335 reads the encoded signaling bit and, if the encoded signaling bit indicates that the low tone was not received, sends a directory number to the scanner 345. The switch 335 connects the scanner 345 to the telephone line 317 so that the alarm service provider can query the STU 310 to determine the problem.
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