Importance

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Abstract

A telemetry device is provided including a dynamic off-hook detector which is capable of determining when a contending telephone device comes off-hook even when the telemetry device is engaged in pulse dialing. The technique is directly applicable to 'current robbing' type dynamic off-hook detectors which sense the current robbed away from the telemetry device when a contending telephone device comes off-hook. The device includes a static off-hook detector or line status indicator for determining when a contending telephone device goes off-hook during the static state of the telemetry device. The dynamic off-hook detector of the telemetry device determines when a contending telephone device goes off-hook while the telemetry device is in the active state, namely while the telemetry device is seizing the phone line for the purpose of communicating collected information to a central station. The telemetry device avoids the problem of pulse dialing interfering with the operation of the dynamic off detector by monitoring the static off-hook indicator during the on-hook portions of the dial pulse. If, during the on-hook portion of the dial pulse, an indication is received that a contending device has gone off-hook, then the dynamic off hook detector of the telemetry device disengages the phone line and returns the telemetry device to the static state.

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First Claim