Telephonic communications – Telephone line or system combined with diverse electrical... – Having transmission of a digital message signal over a...
Patent
1987-10-19
1989-07-25
Ng, Jin F.
Telephonic communications
Telephone line or system combined with diverse electrical...
Having transmission of a digital message signal over a...
379106, 379413, H04M 1100
Patent
active
048521523
ABSTRACT:
A low power consuming signal detection device for attachment to a telephone line. The device has an impedance of at least five megohms across the telephone lines. The device includes a power supply having an input impedance of least five megohms and an amplifier powered by the power supply for amplifying tone interrogation signals present on the telephone line. A phase-locked-loop is responsive to the amplifier signals for determining when the frequency of the amplified signals are within a predefined bandwidth. Phase locking of the phase-locked-loop to the amplified signals is detected by a lock detector when the frequency of the signals falls within a predetermined bandwidth for a predetermined period of time. the lock detection signal is used to place meter reading circuitry in an "off-hook" condition and for effecting the transfer of data from meter data collection apparatus over the telephone line back to a remote location. The signal detection device is solely powered by the normal telephone central office power supply which is applied to the telephone line. Circuitry is provided for temperature compensating the phase-locked-loop to provide a relatively stable source of reference signals for the phase-locked-loop.
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Lancaster, CMOS Cookbook, .COPYRGT.1977, pp. 359-371, 103.
501 Neptune Information Systems
Chan Wing F.
Ng Jin F.
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