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The following specifications and requirements are applicable to the aeronautical facilities referred to in rule 171.53(a)(1)—
(1) each NDB listed in an aeronautical telecommunication service certificate holder’s exposition must conform to the following specification standards, in addition to the specification standards prescribed in ICAO Annex 10, Volume I, section 3.4:
(i) the radiated signal must be either, an uninterrupted carrier amplitude modulated by the on/off keying of a 1020 Hz plus or minus 50 Hz tone, or an uninterrupted carrier identified by the on/off keying of a second carrier separated 1020 Hz plus or minus 50 Hz from the continuous carrier:
(ii) the monitoring functions recommended in paragraphs 3.4.8.2 and 3.4.8.4 of ICAO Annex 10, Volume I are mandatory specification requirements for each NDB aeronautical facility:
(iii) the monitoring system for each NDB aeronautical facility must transmit a warning to a control point and switch off the NDB upon detection of any of the conditions detailed in paragraphs 3.4.8.1 and 3.4.8.2 of ICAO Annex 10, Volume I; and
(2) each UHF DME listed in an aeronautical telecommunication service certificate holder’s exposition must conform with the following requirements, in addition to the specifications prescribed in section 3.5 of ICAO Annex 10, Volume I:
(i) the beacon code identity signal prescribed in paragraph 3.5.3.6.3 (a) of ICAO Annex 10, Volume I must be transmitted at least once but not more than twice every 40 seconds with the code groups equally spaced:
(ii) the monitor function recommended in paragraph 3.5.4.7.2.3 of ICAO Annex 10, Volume I, is a mandatory specification requirement for each DME aeronautical facility; and
(3) each radio navigation aid listed in an aeronautical telecommunication service certificate holder’s exposition must be provided with a monitoring system that will remove the aeronautical facility from operational service and transmit a warning to an appropriate control point upon detection of any of the following conditions:
(i) navigation information outside the prescribed tolerance for the facility:
(ii) failure of the identification signal:
(iii) failure of the monitoring system.
