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6.2.5 Recommendation: The operator should be provided with a degree of assurance that two-way radiotelephony communications for the control of vehicles on the manoeuvring area transmissions have been successful (1116).
NOTE: The normally accepted method of implementing this is to provide off-air sidetone to the operator’s headset. Where UHF Radio Equipment and Systems are used, it may be necessary to provide a separate receiver in addition to the base station receiver, in order to derive the off-air sidetone signal for both directions of transmission.
6.2.6 The operator shall be provided with the facility to select more than one air-ground communications frequency simultaneously (1117). When the PTT control is operated communications shall be transmitted on all selected frequencies to aircraft (1118). When the PTT is released the operator shall be provided with the combined audio signals from all selected frequencies (1119).
NOTE: The operator will normally be provided with off-air sidetone derived from a combination of all the received audio signals from all selected frequencies. It is recognised that the operator is unlikely to be able to determine whether transmissions on each and every selected frequency have been successful; alternative ways of indicating the successful transmissions may be required. It is also acknowledged that the combination of the received audio signals may result in distortion of the overall off-air sidetone. Particular attention may be required in the design and implementation.
6.2.7 Recommendation: When two or more ATS frequencies are being used by a controller, consideration should be given to providing facilities to allow ATS and aircraft transmissions on any of the frequencies to be simultaneously retransmitted on the other frequencies in use thus permitting aircraft stations within range to hear all transmissions to and from the controller (1120).
NOTE: The operator will normally be provided with off-air sidetone derived from only one of the received audio signals. This may be arranged such that the signal paths utilise all the cross-coupled transmit and receive communications channels selected.
6.2.8 The operator shall be provided with the facility to select the state of any available radio channel and an appropriate visual/aural indication shall be given to indicate the selection made (1121).
NOTE: Typical states normally found:
a) Channel off.
b) Channel receive only.
c) Channel transmit and receive.
d) Selection of duplicated transmitters and/or receivers.
e) Selection of Cross-coupling.
6.2.9 The operator shall be provided with a visual/aural indication of the status of available radio channels (1122). NOTE: Typical status reports normally found:
a) Aircraft or vehicle call/receiver mute lift. b) PTT operation.
6.2.10 The delay between operating the PTT control and the appropriate electrical or electronic signal being present at the interface with the VCCS shall be as low as practical (1123).
NOTE: A delay of 20ms or less should be achievable.
6.2.11 The delay between receiving the appropriate electrical or electronic signal at the interface with the VCCS and the activation of any electrical or electronic device, visual or aural indication shall be as low as practical (1124).
NOTE: A delay of 20ms or less should be achievable.
6.2.12 When Air-Ground Communications transmissions to aircraft are in progress, Ground-Ground Communications also in progress at the same time shall not be transmitted to the aircraft (1125). An indication shall be given to the other party that Air-Ground Communications are in progress and this may be achieved by relaying the operators’ speech (1126).
6.2.13 The VCCS shall not fail in a manner such as to cause unintentional or continuous transmissions (1127).
NOTE: The equipment and systems should conform to the 'Minimum Operational Performance Specification for devices that prevent unintentional or continuous transmissions' EUROCAE document ED-67 April 1991, so far as it is appropriate for ground based systems.
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本文链接地址：CAP 670 Air Traffic Services Safety Requirements 2(16)
