Information transmission system with modems coupled to a common communication medium
First Claim
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1. An information transmission system comprising:
- a communication line having a transmission path and a reception path and means for coupling information signals present on said transmission path to said reception path at a predetermined point of said line;
a plurality of information processing devices;
a plurality of modems for coupling said information processing devices to said communication line at arbitrary points thereof and for permitting transmission and reception of information signals among said information processing devices through said communication line, each modem including a transmitting amplifier to transmit an information signal from a corresponding information processing device to said transmission path of said communication line and a receiving amplifier to receive an information signal transmitted to said transmission path by any of said modems through said predetermined coupling point of said transmission and reception paths and said reception path;
a pilot signal providing means for sending out to said communication line a pilot signal of a predetermined reference level which is capable of being received by said receiving amplifier of each of said modems; and
each of said modems further including;
reception level detecting means coupled to said receiving amplifier for detecting the reception level of a signal received through said reception path; and
gain adjusting means responsive to said reception level detecting means for adjusting the gain of said transmitting amplifier such that the reception level of a transmission signal, which is transmitted to said transmission path by said transmitting amplifier and received by said receiving amplifier through said predetermined coupling point of said transmission and reception paths and through said reception path, becomes substantially equal to the reception level of the pilot signal received by said receiving amplifler.
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Abstract
A plurality of information processors are coupled by respective modems to a communication medium at points thereof. Transmission and reception of information signals among the modems are effected through a headed located at a predetermined point on the communication medium. A pilot signal generator is provided which sends out a pilot signal having a predetermined reference level through the headend to the communication medium. Each modem is arranged to properly adjust the gain of its transmitting amplifier according to a reception level of the pilot signal for an improvement of signal transmission quality and a reliable detection of a signal collision.
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Citations
30 Claims
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1. An information transmission system comprising:
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a communication line having a transmission path and a reception path and means for coupling information signals present on said transmission path to said reception path at a predetermined point of said line; a plurality of information processing devices; a plurality of modems for coupling said information processing devices to said communication line at arbitrary points thereof and for permitting transmission and reception of information signals among said information processing devices through said communication line, each modem including a transmitting amplifier to transmit an information signal from a corresponding information processing device to said transmission path of said communication line and a receiving amplifier to receive an information signal transmitted to said transmission path by any of said modems through said predetermined coupling point of said transmission and reception paths and said reception path; a pilot signal providing means for sending out to said communication line a pilot signal of a predetermined reference level which is capable of being received by said receiving amplifier of each of said modems; and each of said modems further including; reception level detecting means coupled to said receiving amplifier for detecting the reception level of a signal received through said reception path; and gain adjusting means responsive to said reception level detecting means for adjusting the gain of said transmitting amplifier such that the reception level of a transmission signal, which is transmitted to said transmission path by said transmitting amplifier and received by said receiving amplifier through said predetermined coupling point of said transmission and reception paths and through said reception path, becomes substantially equal to the reception level of the pilot signal received by said receiving amplifler. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An information transmission system comprising:
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a communication line having a transmission path and a reception path and means for coupling information signals present on said transmission path to said reception path at a predetermined point of said line; a plurality of information processing devices; a plurality of modems for coupling said information processing devices to said communication line at arbitrary points thereof and for permitting transmission and reception of information signals among said information processing devices through said communication line, each modem including a transmitting amplifier to transmit an information signal from a corresponding information processing device to said transmission path of said communication line and a receiving amplifier to receive an information signal transmitted to said transmission path by any of said modems through said predetermined coupling point of said transmission and reception paths and said reception path; a pilot signals providing means for sending out to said communication line a pilot signal of a predetermined reference level which is capable of being received by said receiving amplifier of each of said modems; and each of said modems further including; reception level detecting means coupled to said receiving amplifier for detecting the reception level of a signal received through said reception path; and gain adjusting means responsive to said reception level detecting means for adjusting the gain of said transmitting amplifier such that the reception level of a transmission signal, which is transmitted to said transmission path by said transmitting amplifier and received by said receiving amplifier through said predetermined coupling point of said transmission and reception paths and through said reception path, becomes a predetermined level which is a function of the reception level of the pilot signal received by said receiving amplifier.
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9. An information transmission system comprising:
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a communication line having a transmission path and a reception path and means for coupling information signals present on said transmission path to said reception path at a predetermined point of said line; a plurality of information processing devices; a plurality of modems for coupling said information processing devices to said communication line at arbitrary points thereof and for permitting transmission and reception of information signals among said information processing devices through said communication line, each modem including a transmitting amplifier to transmit an information signal from a corresponding information processing device to said transmission path of said communication line and a receiving amplifier to receive an information signal transmitted to said transmission path by any of said modems, through said predetermined coupling point of said transmission and reception paths and through said reception path; a pilot signal providing means for sending out to said coupling point of said communication line a pilot signal of a predetermined reference level which is capable of being received by said receiving amplifier of each of said modems; and each of said modems further including; reception level detecting means coupled to said receiving amplifier for detecting the reception level of a signal received through said reception path; and gain adjusting means responsive to said reception level detecting means for adjusting the gain of said transmitting amplifier such that a transmission signal, which is transmitted to said transmission path by said transmitting amplifier, has, at said coupling point of said communication line, a predetermined level which is a function of the reference level of the pilot signal at said coupling point.
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10. An information transmission system comprising:
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a communication line having a transmission path and a reception path and means for coupling information present on said transmission path to said reception path at a predetermined point of said line; a plurality of information processing devices; a plurality of modems for coupling said information processing devices to said communication line at arbitrary points thereof and for permitting transmission and reception of information signals among said information processing devices through said communication line, each modem including a transmitting amplifier to transmit an information signal from a corresponding information processing device to said transmission path of said communication line and a receiving amplifier to receive an information signal transmitted to said transmission path by each of said modems, through said predetermined coupling point of said transmission and reception paths and through said reception path; a pilot signal sending means for sending out to said communication line an unmodulated pilot signal of a predetermined reference level which is capable of begin received by said receiving amplifier of each of said modems; and each of said modems further including; reception level detecting means coupled to said receiving amlifier for detecting the reception level of a signal received through said reception path; test signal sending means for sending an unmodulated test signal to said transmission path through said transmitting amplifier; unmodulated signal detecting means for detecting that a signal received by said receiving amplifier is the pilot signal or the test signal; and gain adjusting means responsive to said reception level detecting means and said unmodulated signal detecting means for, when the reception level of the pilot signal received by said receiving amplifier is detected, causing said test signal sending means to send out a test signal to said transmission path and adjusting the gain of said transmitting amplifier such that the reception level of the test signal received by said receiving amplifier through said predetermined point of said communication line becames substantially equal to the reception level of the pilot signal received by said receiving amplifier. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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18. An information transmission system comprising:
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a communication line having a transmission path and a reception path and means for coupling information signals present on said transmission path to said reception path at a predetermined point of said line; a plurality of information processing devices; a plurality of modems for coupling said information processing devices to said communication line at arbitrary points thereof and for permitting transmission and reception of information signals among said information processing devices through said communication line, each modem including a transmitting amplifier to transmit an information signal from a corresponding information processing device to said transmission path of said communication line and a receiving amplifier to receive an information signal transmitted to said transmission path by each of said modems through said predetermined coupling point of said transmission and reception paths and through said reception path; reception level detecting means coupled to said receiving amplifier for detecting the reception level of a signal received through said reception path; and gain adjusting means responsive to said reception level detecting means for adjusting the gain of said transmitting amplifier such that the reception level of a transmission signal, which is transmitted to said transmission path by said transmitting amplifier and received by said receiving amplifier through said predetermined coupling point of said transmission and reception paths and through said reception path, becomes substantially equal to the reception level of a signal transmitted from another modem and received by said receiving amplifier. - View Dependent Claims (19, 20, 21, 22, 23, 24)
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25. In an information transmission system comprising a communication line having a transmission path and a reception path and means for coupling information signals present on said transmission path to said reception path at a predetermined point of said line, a plurality of information processing devices, a plurality of modems for coupling said information processing devices to said communication line at arbitrary points thereof and for effecting information transmission among said information processing devices through said communication line, each modem including a transmitting amplifier to transmit an information signal from a corresponding information processing device to said transmission path of said communication line, and a receiving amplifier to receive an information signal transmitted to said transmission path by any of said modems through said coupling point of said transmission and reception paths and through said reception path, a method of causing each of said modems to receive information signals from other modems at a substantially constant level, comprising the steps of:
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providing a pilot signal of a reference level to a predetermined point of said communication line; detecting the reception level of the pilot signal received by said receiving amplifier; sending a transmission signal to said communication line through said transmitting amplifier; receiving the transmission signal sent out to said communication line by said receiving amplifier through said coupling point of said communication line and said reception path; and adjusting the gain of said transmitting amplifier such that the reception level of the transmission signal received by said receiving amplifier becomes substantially equal to the reception level of the pilot signal received by said receiving amplifier. - View Dependent Claims (26, 27, 28, 29)
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30. In an information transmission system comprising a communication line having a transmission path and a reception path and means for coupling information signals present on said transmission path to said reception path at a predetermined point of said line, a plurality of information processing devices, a plurality of modems for coupling said information processing devices to said communication line at arbitrary points thereof and for effecting information transmission among said information processing devices through said communication line, each modem including a transmitting amplifier to transmit an information signal from a corresponding information processing device to said transmission path of said communication line, and a receiving amplifier to receive an information signal transmitted to said transmission path by any of said modems through said coupling point of said transmission and reception paths and through said reception path, a method of causing each of said modems to receive information signals from other modems at a substantially constant level, comprising the steps of:
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receiving by said receiving amplifier an information signal transmitted from a predetermined modem to said communication line through said coupling point of said communication line and said reception path; detecting the reception level of the information signal from said predetermined modem received by said receiving amplifier; transmitting a transmission signal to said communication line through said transmitting amplifier; receiving the transmission signal by said receiving amplfier through said coupling point of said communication line and said reception path; and adjusting the gain of said transmitting amplifier such that the reception level of the transmission signal becomes substantially equal to the reception level of the information signal transmitted from said predetermined modem.
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Specification