Telecommunications – Transmitter and receiver at same station – With transmitter-receiver switching or interaction prevention
Patent
1994-12-05
1996-10-15
Faile, Andrew I.
Telecommunications
Transmitter and receiver at same station
With transmitter-receiver switching or interaction prevention
455 582, 455 98, H04B 144
Patent
active
055663591
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION--FIELD OF THE INVENTION
The present invention relates to ground transmitting and receiving apparatus and more particularly to means for preventing simultaneous transmission between two or more of such apparatus.
DESCRIPTION OF THE PRIOR ART
UK Patent No. 2083979, in the name of the present applicant, describes a means of blocking the operation of a second radio transmitter when a first transmitter is occupying the frequency, the purpose being to prevent coincident and conflicting transmissions in a simplex radio network. The effectiveness of such an arrangement, in preventing coincident transmissions, depends on certain variables such as the time for the first transmitter to produce RF energy following a press-to-transmit action, and the time for the blocking apparatus of the second receiver to detect this energy. If the second press-to-transmit is made prior to detection of RF resulting from the first then a Conflict of both transmissions will result. The longer these delays then the less effective the conflict prevention system. In semi-duplex Air Traffic Control ground installations, where a full time receiver monitors associated transmitter operation, land lines are frequently used to transfer control and voice signals from a remote operators site. These land lines and their associated switching apparatus introduce relatively lengthy delays which adversely influence the effectiveness of the apparatus of UK Patent No. 2083979. A means of minimising the effect of any such delays would improve the apparatus of UK Patent No. 2083979 when applied to semi-duplex radio systems. In essence,: such an arrangement may have stored, in electronic memory, the detected time period between press-to-transmit application and consequent response of the associated receiver. In operation, any receiver response following a press-to-transmit action, but which occurs before the stored time period has expired, must be from an RF source which has preceded that from the associated transmitter. In this case it is beneficial to prevent, or terminate, operation of the associated transmitter, thereby allowing the preceding radio signal to be monitored without disruption.
SUMMARY OF THE INVENTION
Accordingly, and distinguished over UK Patent No. 2083979, the present invention provides a means of electronically determining the time period between a press-to-transmit application and subsequent receiver response of the equipment in which the invention is incorporated, a means of electronically storing this time period less a proportion, say 10%, a means of initiating the resultant time period at application of a press-to-transmit action, a means of monitoring the expiry of the time period, and a means of disconnecting the press-to-transmit control signal from the transmitter when subsequent receiver activity is detected prior to expiry of the known period.
The present invention provides apparatus for preventing simultaneous transmitter operation in a radio transmitting and receiving apparatus comprising means for detecting the commencement at a control position of a transmission control switch operation (PTT) in said apparatus, means for starting a timer, means for detecting the receipt at the control position of a signal received by said receiver of said apparatus, means for disabling the transmitter if the receipt of the signal at the control position occurs within a predetermined time interval from the commencement of transmission, and in which there is provided means for deriving the predetermined time interval comprising which comprises means for switching on the transmitter of said apparatus at the control position to generate a transmission signal, means for activating the timer at the time of switching on of the transmitter, means for detecting at the control position the transmission signal received as a result of the transmitter operation, means for storing the time period between switching on of the transmitter and the reception of the transmission signal at the control position, and means f
REFERENCES:
patent: 4494244 (1985-01-01), Arndt et al.
patent: 4549309 (1985-10-01), Corrigan
patent: 4551854 (1985-11-01), Rutty et al.
patent: 4932071 (1990-06-01), Arndt
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