Remote automatic reading system
First Claim
1. In combination with a sensor at a data reading station detecting a sequence of events to produce corresponding switch closures, and a telephone communication system having message lines, through which polling signals are transmitted to said data reading station for interrogation thereof and data signals from the data reading station are transmitted to a data collecting station, an automatic reading unit comprising digital logic means connected to the sensor for storing digital input data in response to said switch closures, interrogation input means coupling the message lines to the digital logic means for transforming said stored digital input data into a frequency shifted, step simulated sinusoidal waveform in response to a coded analog polling signal, digital-to-analog converter means coupling said digital logic means to the message lines for converting said transformed digital input data into an analog data signal transmitted by the message lines to the data collecting station, a source of AC power connected to the automatic reading unit for operation thereof independently of the telephone communication system and an auxiliary source of DC power for operating the automatic reading unit in response to loss of power from the AC power source, said digital input data having a format including data bits corresponding to said switch closures and a power sensing bit representing the state of the AC power source.
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Abstract
Utility or industrial meters having rotating elements are monitored by an automatic reading unit through which digital input data is stored and read out in response to interrogation by a coded polling signal transmitted to the unit through telephone lines. Readout occurs during a transmit cycle and includes the serial transfer of stored digital data to digital synthesizers through which data is converted to a sinusoidal analog signal transmitted by the telephone lines for decoding at a data collecting station. By the addition of optional components, time of day metering, demand metering and the exercise of control functions at a remote site may be effected.
40 Citations
13 Claims
- 1. In combination with a sensor at a data reading station detecting a sequence of events to produce corresponding switch closures, and a telephone communication system having message lines, through which polling signals are transmitted to said data reading station for interrogation thereof and data signals from the data reading station are transmitted to a data collecting station, an automatic reading unit comprising digital logic means connected to the sensor for storing digital input data in response to said switch closures, interrogation input means coupling the message lines to the digital logic means for transforming said stored digital input data into a frequency shifted, step simulated sinusoidal waveform in response to a coded analog polling signal, digital-to-analog converter means coupling said digital logic means to the message lines for converting said transformed digital input data into an analog data signal transmitted by the message lines to the data collecting station, a source of AC power connected to the automatic reading unit for operation thereof independently of the telephone communication system and an auxiliary source of DC power for operating the automatic reading unit in response to loss of power from the AC power source, said digital input data having a format including data bits corresponding to said switch closures and a power sensing bit representing the state of the AC power source.
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11. In combination with a source of digital input data and signal transmitting means through which an analog polling signal is transmitted, an automatic reading unit interconnected between said source and the signal transmitting means, comprising digital counter logic connected to the source for storing the input data, demodulating means connected to the signal transmitting means for transforming said analog polling signal into a digital poll code, data processing means connected to said digital counter logic for serial readout of the stored input data during a transmitting cycle, transmit control means connected to the interrogation means for initiating said transmitting cycle in response to said digital poll code and converter means connected to the data processing means for converting the readout of the stored input data into an analog data signal fed to the signal transmitting means, said data processing means including means for producing a zero output at the beginning of the transmitting cycle for a zero fill period before said readout of the stored input data.
Specification