-SL-23-043 REV. A VHF-920 DATA RADIO (822-1250-002) - MODE LOCK-UP CONDITION. SERVICE LETTER MOS 09-JUL-2009 SL 737-SL-23-044 NOISE ON SERVICE INTERPHONE. SERVICE LETTER MOS I9-JAN-2010 SL 737-SL-23-044 REV. A NOISE ON SERVICE INTERPHONE (SUPERSEDED BY 737-SL-23-044-B). SERVICE LETTER MOS 26-JAN