Remote meter reading
First Claim
1. A remote meter reading system, comprising an encoder for association with a meter and a portable reader, the encoder having power terminal means for connection with a source of electrical power in the reader generating a periodic power signal and adapted when power by said signal to derive a digital encoding of the meter reading for transmission to the reader, wherein the encoder comprises impedance switch means serving to vary the input impedance at the power terminal means in representation of the digital encoding to provide a voltage variation detectable at said power source, said encoder comprising a frequency reference controlling the timing of said impedance switch means so that the operation of said impedance switch means is asynchronous with the power signal and there is no synchronous relationship required between the power signal and data transmitted from the encoder to the reader.
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Accused Products
Abstract
A remote meter reading system, for example for domestic water meters, operates through an inductive coupling over two lines. A sinusoidal power signal is transmitted from a reader to the meter to power up encoding circuitry in the meter. The encoding circuitry then transmits data by intermittently shorting the input terminals to cause an asynchronous voltage modulation at the reader. There is no synchronous relationship required between the periodic power signal and the data transmitted from the encoder to the reader.
68 Citations
14 Claims
- 1. A remote meter reading system, comprising an encoder for association with a meter and a portable reader, the encoder having power terminal means for connection with a source of electrical power in the reader generating a periodic power signal and adapted when power by said signal to derive a digital encoding of the meter reading for transmission to the reader, wherein the encoder comprises impedance switch means serving to vary the input impedance at the power terminal means in representation of the digital encoding to provide a voltage variation detectable at said power source, said encoder comprising a frequency reference controlling the timing of said impedance switch means so that the operation of said impedance switch means is asynchronous with the power signal and there is no synchronous relationship required between the power signal and data transmitted from the encoder to the reader.
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8. A remote meter reading system, comprising an encoder for association with a meter and a reader, the encoder having power terminal means for connection with the reader and adapted when powered to derive a digital encoding of the meter reading for transmission to the reader, wherein the encoder comprises switch means serving intermittently to short the power terminal means in representation of the digital encoding;
- and wherein the reader comprises a power source adapted to generate a periodic power signal; and
detector means for detecting an asynchronous voltage modulation in said power signal consequent upon said intermittent shorting of the encoder power terminal means. - View Dependent Claims (9, 10, 11, 12, 13, 14)
- and wherein the reader comprises a power source adapted to generate a periodic power signal; and
Specification