Data transmission circuit for an electricity mains network having a low reception threshold
First Claim
1. A data transmission circuit, for use on a mains electricity network, includes a circuit that supplies a first signal that indicates one of when the network is occupied and when the network is not occupied based upon a comparison between a level of a received signal and a predetermined threshold value and means for indicating one of a receive mode and a transmit mode, includes a digital circuit that supplies a second signal different from the first signal that indicates one of occupation of the network and non-occupation of the network based on identification of a predetermined data sequence that is present before a data message within the received signal on the network and means for indicating the transmit mode when said first and second signals each indicates the network is not occupied.
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Accused Products
Abstract
The invention concerns a data transmission circuit, for use on a mains electricity network, that includes a modulator/ demodulator circuit that supplies a first signal, which indicates if the network is occupied, that is based upon a comparison between the level of a received signal and a predetermined threshold value and circuitry for switching a modem into its receive mode or its transmit mode, including a digital circuit that supplies a second signal that indicates the occupation of the network based on the identification of a predetermined data sequence that is present within each transmission stream before a data message and circuitry for allowing the modem to switch to its transmit mode when the occupation signals indicate an absence of a transmission.
6 Citations
24 Claims
- 1. A data transmission circuit, for use on a mains electricity network, includes a circuit that supplies a first signal that indicates one of when the network is occupied and when the network is not occupied based upon a comparison between a level of a received signal and a predetermined threshold value and means for indicating one of a receive mode and a transmit mode, includes a digital circuit that supplies a second signal different from the first signal that indicates one of occupation of the network and non-occupation of the network based on identification of a predetermined data sequence that is present before a data message within the received signal on the network and means for indicating the transmit mode when said first and second signals each indicates the network is not occupied.
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9. A system for detecting a data message on a mains electricity network, the system comprising:
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an input lead to receive a modulated signal; a level detecting circuit coupled to the input lead, the level detecting circuit to output a level detect signal having a first state indicating an absence of a transmission signal on the network and a second state indicating a presence of the transmission signal; a demodulator coupled to the input lead, the demodulator to output a demodulated signal at a demodulator output; a sequence detector coupled to the demodulator output, the sequence detector to output a sequence detect signal having a third state indicating detection of a predetermined data sequence and a fourth state indicating non-detection of the predetermined data sequence; and a digital circuit to receive the level detect signal and the sequence detect signal, the digital circuit to determine a data message has been detected when the level detect signal is in the second state and the sequence detect signal is in the third state at a same time. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. A system for detecting a data message on a mains electricity network carrying a modulated signal, the system comprising:
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first means for receiving the modulated signal; means for comparing a modulated signal level of the modulated signal to a predetermined threshold level and generating a level comparison signal when the modulated signal level is at least the threshold level; means for generating a demodulated signal from the modulated signal; second means for detecting a predetermined data sequence in the demodulated signal and for outputting a sequence detect signal at one of a first level when the predetermined data sequence has been detected and a second level when the predetermined data sequence has not been detected; and third means for determining the data message has been detected when the sequence detect signal is at the first level and the level comparison signal is present, otherwise determining that the data message has not been detected. - View Dependent Claims (18, 19, 20)
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21. A method for detecting when a mains electricity network is available for transmitting a data message, the method comprising the steps of:
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(a) receiving a modulated signal on the network; (b) comparing a modulated signal level of the modulated signal to a predetermined threshold level; (c) generating a level comparison signal in a first state when said step (b) indicates the network is available; (d) generating the level comparison signal in a second state when said step (b) indicates the network is not available; (e) demodulating the modulated signal to create a demodulated signal; (f) determining whether or not a predetermined data sequence is found in the demodulated signal; and (g) when the predetermined data sequence has been found in the demodulated signal and the level comparison signal is in the second state, indicating that the mains electricity network is not available, otherwise indicating that the mains network is available. - View Dependent Claims (22, 23, 24)
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Specification