TO: ALL AIRWAY FACILITIES DIVISION MANAGERS
ATTN: AIRWAY FACILITIES SECTOR MANAGERS
SUBJ: LOSS OF BEACON VIDEO WHEN POWER CYCLING STANDBY
INTERROGATOR FOR MODE S IN INDEPENDENT BEACON INTERROGATOR
(IBI) MODE
TWX: TWX-MODES-3001
DATE: 10/20/93
TWO MODE S (IBI) FACILITIES REPORTED LOSS OF BEACON VIDEO FROM
THE ONLINE INTERROGATOR WHEN THE MAIN POWER WAS CYCLED OFF/ON ON
THE STANDBY INTERROGATOR. THIS OCCURRED WHEN FOLLOWING THE
PROCEDURES IN MEASURING THE RECEIVER SENSITIVITY AND STC,
ACCORDING TO PARAGRAPH 156 IN THE DRAFT MAINTENANCE HANDBOOK
6360.XX (6365.XX). THIS CAN OCCUR WITH ANY POWER OFF/ON CYCLE OF
THE STANDBY INTERROGATOR.
THE CAUSE IS A POWER ON GLITCH FROM CERTAIN VSWR MONITOR BOARDS
(A116) IN THE INTERROGATOR, CAUSING THE VIDEO TRIGGER DRIVER
BOARD IN THE MODE S JUNCTION BOX (MSJB) TO SELECT THE WRONG
CHANNEL'S OUTPUT VIDEO.
UNTIL FINAL RESOLUTION OF THIS PROBLEM, IT IS SUGGESTED THAT
SCHEDULED DOWN TIME BE REQUESTED TO ASCERTAIN IF THIS PROBLEM
EXISTS IN EITHER CHANNEL. IF THE CONDITION DOES EXIST AT YOUR
FACILITY, PLEASE ADVISE AOS-500. FURTHER, IF THE CONDITION DOES
EXIST AT YOUR FACILITY, IT IS RECOMMENDED THAT SCHEDULED DOWN TIME
BE REQUESTED WHEN PERFORMING ANY FUTURE MAINTENANCE WHICH REQUIRES
POWER ON/OFF CYCLING OF THE STANDBY MODE S INTERROGATOR.
IF YOU HAVE ANY FURTHER QUESTIONS REGARDING THIS MESSAGE, PLEASE
CONTACT AOS-500 ON (609) 485-HELP.
EDWARD J. SCHUMAN
MANAGER, NATIONAL DATA COMMUNICATIONS
SYSTEMS ENGINEERING DIVISION, A0S-500