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- Path: sparky!uunet!zephyr.ens.tek.com!master!pendragon!tonyo
- From: tonyo@pendragon.CNA.TEK.COM (Tony Ozrelic)
- Newsgroups: sci.electronics
- Subject: Re: Aeroplane Seat Boxes for entertainment (was Re: SHOCKING STORIES)
- Message-ID: <3255@master.CNA.TEK.COM>
- Date: 29 Jul 92 19:24:25 GMT
- References: <3217@master.CNA.TEK.COM> <l79uohINNr7m@appserv.Eng.Sun.COM>
- Sender: news@master.CNA.TEK.COM
- Organization: Tektronix, Inc., Redmond, OR.
- Lines: 37
-
- In article <l79uohINNr7m@appserv.Eng.Sun.COM> bender@oobleck.eng.sun.com writes:
- >>Another time I was working as a repair tech on seat boxes (the gizmos under
- >>your airplane seat that pipe music to you [...]
- >
- >Can give some more detail on how these work? Do the planes have one large
- >multitrack tape for all of the entertainment channels?
- >
-
- The name of the company was Telephonics, and the system was used on 747's and
- L-1011s. Thirteen channels of audio (12 stereo, 1 PA, 1 intercom). Near the
- front of the plane was 12 continous-loop tape players that fed into a box
- that digitized the sound at 8kHz (or was it 12?), put it onto a serial line
- (Time Division multiplexing, can't remember the frame rate), and daisy-chained
- it to every seat on the plane. The seat boxes also had switches for lights
- and stewardess call. These signals were multiplexed onto the line too, and
- there was a little box in the overhead that controlled the lighting for your
- seat depending on your switch setting.
-
- This all worked real nice, but when the Zone Submultiplexers that controlled
- the lighting went out, an entire row of lights would blink on and off all
- at the same time. Then they would flip the breaker and no lights and no
- sound!
-
- The other thing that was controlled by the overhead boxes was the dropping of
- the oxygen masks. A glitch here or there in the ZSs would cause all the masks
- in a row to fall out at once. Needless to say, this would freak out passengers!
-
- All this was done to save weight, as all you needed was one cable that had
- power and this spiffy TDM signal. All the boxes had custom MOS/LSI stuff
- in them. Telephonics (a division of Instrument Systems Corp) thought they would
- make a bundle on service contracts to offset the expense of the system. What
- they didn't count on was the horrendous environmental problems involved in
- these boxes - high temperature, soda, vomit, gorilla service people, etc.
-
- Anybody out there know whatever became of ISC/Telephonics?
-
- tony "a TENSE workplace is a PRODUCTIVE workplace" o.
-