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4.4  Recording and Replay Quality
4.4.1  The voice quality obtained during replay of recorded radio communication between ATC and aircraft under their control shall be equal to or better than the Mean Opinion Score (MOS) required in paragraph 4.1.1.1 (2270).
NOTE:  Manufacturers are encouraged to consult the Recommendations published by the International Telecommunications Union (ITU) as P.862. The technique described in P.862 is an enhanced perceptual quality measurement of voice quality in telecommunications known as PESQ (Perceptual Evaluation of Speech Quality). The PESQ algorithm is protected by patents and was jointly developed by British Telecommunications plc and Royal KPN NV (www.pesq.org).
PESQ provides rapid and repeatable results without the need for the listening panel tests usually needed to establish a Mean Opinion Score (MOS).
Several manufacturers are now able to offer test equipment or software based tools capable of determining PESQ but it must be remembered that ATC radio communications usually consist of several brief and rapid exchanges, the quality of which may vary greatly during typical operations. In contrast, the quality of operational telephone conversations that must also be recorded will generally conform to commercial standards.
The latest Recommendation, P.862.1, provides an improved correlation to MOS and in tests conducted using P.862.1, a proprietary codec operating at 8 kbits/second produced consistently better results than a legacy codec operating at 16 kbits/second.
COM 02 VHF Aeronautical Radio Stations Part 1 Preliminary Material
1  Introduction 
1.1  Under the terms of Article 205 of the Air Navigation Order, any Air Traffic Service equipment is required to have CAA approval before being established or used in the United Kingdom. Under the terms of Article 255 an Aeronautical Radio Station is specifically included in the meaning of Air Traffic Service Equipment. 
NOTE:  The term 'Aeronautical Radio Station' in the definitions contained in the Glossary, is taken to include the terms Aeronautical Station and Aeronautical Mobile Station for the purposes of this document. 
2  Scope 
2.1  This document sets out the engineering requirements for VHF radio equipment and systems at Aeronautical Radio Stations of the Aeronautical Mobile Service established or used within the United Kingdom to provide Air Traffic Services. 
NOTE:  ‘Air Traffic Services’ means the various flight information services, alerting services, air traffic advisory services and ATC services (area, approach and aerodrome control services). One or more of these services may be employed in the En-Route Communications Network, at Area Control Centres, and Aerodromes. 

2.2  This document applies to fixed, stationary, vehicle, portable and hand held equipment categories comprising transmitter, receiver and transceiver equipment types operating in the VHF Aeronautical Mobile (R) Service allocation 118 MHz to 136.975 MHz, using Double Sideband (DSB) Amplitude Modulation (AM) full carrier with 8.33 kHz or 25kHz channel spacing, intended for analogue voice and data link communications.
Definitions and abbreviations
3.1 Definitions
A
Aeronautical Mobile Station
C
Contingency Equipment
D
Designated Operational Coverage
E
Emergency Equipment
Equipment Categories
Equipment Redundancy
Equipment Types A Station in the Aeronautical Mobile Service, other than an Aircraft Station, intended to be used while in motion or during halts at unspecified points. [Based on ITU RR S1.32, S1.67 & S1.73 and ICAO Annex 10 Volume II Chapter 1]
Equipment which is used for business continuity purposes.
Designated Operational Coverage (DOC) is that volume of airspace needed operationally in order to provide a particular service and within which the facility is afforded frequency protection. [ITU RR S45.1.1] The DOC is quantified by operational range in nautical miles and height in flight level or feet above ground level and defines the limit of the service area associated with the frequency assignment for a particular service. See Radio Service Area.
　
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