US4376310A
Expired / Lapsed
US
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Mobile data terminal channel busy arrangement
Assignee: Ericsson Inc
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Filing: 1981-05-13
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Granted: 1983-03-08
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Expires: 2001-05-13
Abstract
Abstract A channel busy arrangement for use in a radio-based data transmission system comprising a plurality of data terminals. A carrier activity signal (CAS) generated by a receiver associated with a data terminal is used to trigger a CAS pulse of approximately 300 msec. A demodulated audio signal from the receiver is coupled to a SYNC detector for detecting a data synchronizing (SYNC) signal generally transmitted before a data message and to an optional continuous tone coded squelch system (CTCSS) for generating a CTCSS signal. The CAS pulse, SYNC signal and CTCSS signal are logic ORed to generate a channel busy signal used for inhibiting data transmission. Thus, data transmission is inhibited only during a 300 msec CAS pulse, when a SYNC signal is present, or during valid non-data transmissions (voice) even in the presence of an interfering signal.
Inventors
- 👤 Bill L. Stackhouse
- 👤 Theodore E. Taylor
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 02:06
CPC Classifications
H; H04; H04L; H04L1/00; H04L1/20; H03; H03G; H03G3/00; H03G3/005; H04L7/00; H04L7/04
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
144 words
An arrangement, for use with a data terminal capable of transmitting or receiving a digital data message including a data synchronizing signal, for determining the busy/free status of a radio channel, comprising: a radio receiver providing (a) a demodulated audio signal and (b) a carrier activated switch (CAS) signal indicating the presence of a carrier signal or noise on the radio channel; a SYNC detector, for generating, in response to said demodulated audio signal, a SYNC signal whenever said demodulated audio signal includes said data synchronizing signal; a pulse generator, for generating, in response to said CAS signal, a CAS pulse having a predetermined duration; and logic OR function means for generating a channel busy signal responsive to the presence of either said SYNC signal or said CAS pulse, said channel busy signal for inhibiting transmission of a data message by said data terminal.
Claim 2
Dependent Claim
144 words
An arrangement, for use with a data terminal capable of transmitting or receiving a digital data message including a data synchronizing signal, for determining the busy/free status of a radio channel, comprising: a radio receiver providing (a) a demodulated audio signal and (b) a carrier activated switch (CAS) signal indicating the presence of a carrier signal or noise on the radio channel; a SYNC detector, for generating, in response to said demodulated audio signal, a SYNC signal whenever said demodulated audio signal includes said data synchronizing signal; a pulse generator, for generating, in response to said CAS signal, a CAS pulse having a predetermined duration; and logic OR function means for generating a channel busy signal responsive to the presence of either said SYNC signal or said CAS pulse, said channel busy signal for inhibiting transmission of a data message by said data terminal.
Claim 3
Dependent Claim
76 words
An arrangement according to claim 1 further including a continuous tone coded squelch system (CTCSS) for generating, responsive to said demodulated audio signal, a receiver unsquelch (RUS) signal, said RUS signal being logically OR gated with said SYNC signal and said CAS pulse by said logic OR function means, said CTCSS for use with radio systems wherein voice transmission is used in addition to digital data transmission, said CTCSS detecting the presence of valid non-data transmissions.
Claim 4
Dependent Claim
35 words
An arrangement according to either claim 1 or claim 2 wherein said pulse generator generates said CAS pulse so as to have a leading edge substantially coinciding with a leading edge of said CAS signal.
Claim 5
Dependent Claim
17 words
An arrangement according to claim 3 wherein the duration of said CAS pulse is substantially 300 milliseconds.
Claim 6
Dependent Claim
178 words
In a data transmission system wherein data terminals transmit digital data messages including a synchronizing signal and digital data modulated on a carrier signal over a radio channel and wherein a receiver, associated with a data terminal, receives a digital data message, demodulates to produce a demodulated audio signal and generates a carrier activated switch (CAS) signal indicative of a carrier or noise on the radio channel indicating that the channel is busy, said CAS signal being utilized to inhibit data transmission by the data terminal, the improvement comprising: providing a pulse generator for generating, in response to said CAS signal, a CAS pulse having a predetermined duration; a SYNC detector for generating a SYNC signal whenever said receiver detects a synchronizing signal; and logic OR function means responsive to said CAS pulse and to said SYNC signal for inhibiting data transmission for an interval of time corresponding to the duration of said CAS pulse while determining whether a SYNC signal will appear or not and providing a channel busy signal extending beyond the duration of SYNC signal.
Claim 7
Dependent Claim
178 words
In a data transmission system wherein data terminals transmit digital data messages including a synchronizing signal and digital data modulated on a carrier signal over a radio channel and wherein a receiver, associated with a data terminal, receives a digital data message, demodulates to produce a demodulated audio signal and generates a carrier activated switch (CAS) signal indicative of a carrier or noise on the radio channel indicating that the channel is busy, said CAS signal being utilized to inhibit data transmission by the data terminal, the improvement comprising: providing a pulse generator for generating, in response to said CAS signal, a CAS pulse having a predetermined duration; a SYNC detector for generating a SYNC signal whenever said receiver detects a synchronizing signal; and logic OR function means responsive to said CAS pulse and to said SYNC signal for inhibiting data transmission for an interval of time corresponding to the duration of said CAS pulse while determining whether a SYNC signal will appear or not and providing a channel busy signal extending beyond the duration of SYNC signal.
Claim 8
Dependent Claim
76 words
An improvement according to claim 5 further comprising a continuous tone coded squelch system (CTCSS) for generating, responsive to said demodulated audio signal, a receiver unsquelch (RUS) signal, said RUS signal being logically OR gated with said SYNC signal and said CAS pulse by said logic OR function means, said CTCSS for use with radio systems wherein voice transmission is used in addition to digital data transmission, said CTCSS detecting the presence of valid non-data transmissions.
Claim 9
Dependent Claim
33 words
An improvement according to claim 5 or 6 wherein said pulse generator generates said CAS pulse so as to have a leading edge substantially coinciding with a leading edge of said CAS signal.
Claim 10
Dependent Claim
17 words
An improvement according to claim 7 wherein the duration of said CAS pulse is substantially 300 milliseconds.
Claim 11
Independent Claim
141 words
A method for determining the busy/free status of a radio channel used for transmission by a data terminal of a data message including synchronizing signals and data signals modulated on a carrier signal, comprising: first detecting, with a radio receiver, a signal from said radio channel to provide (a) a demodulated audio signal and (b) a carrier activated switch (CAS) signal indicating the presence of a carrier signal or noise on the radio channel; second generating, in response to said audio signal, a SYNC signal whenever said audio signal includes a data synchronizing signal as part of a digital data message; third generating, in response to said CAS signal, a CAS pulse having a predetermined duration; and OR-gating said SYNC signal and said CAS pulse to generate a channel busy signal for inhibiting the transmission of data by said data terminal.
Claim 12
Independent Claim
141 words
A method for determining the busy/free status of a radio channel used for transmission by a data terminal of a data message including synchronizing signals and data signals modulated on a carrier signal, comprising: first detecting, with a radio receiver, a signal from said radio channel to provide (a) a demodulated audio signal and (b) a carrier activated switch (CAS) signal indicating the presence of a carrier signal or noise on the radio channel; second generating, in response to said audio signal, a SYNC signal whenever said audio signal includes a data synchronizing signal as part of a digital data message; third generating, in response to said CAS signal, a CAS pulse having a predetermined duration; and OR-gating said SYNC signal and said CAS pulse to generate a channel busy signal for inhibiting the transmission of data by said data terminal.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1986-03-07 | 1986-09-06 | 1987-03-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-03-07 | 1990-09-06 | 1991-03-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-03-07 | 1994-09-06 | 1995-03-08 | $7700.00 | Window Closed / Lapsed |