On a few occasions over the past decade, I've been watching television
(the MacaNeil-Lehrer news hour, usually) when Morse code (audio -
high-pitched, not too loud) has been broadcast for a minute or two,
overlaid with the show's normal sounds.
  I'm not talking about the loud intro-music that some programs have,
where "dah dit dit-dit dit dit dit-dit..." is played to indicate that
news is coming up; this was quieter, prolonged, and simultaneous with
dialogue.

What is this all about?

---

Clarification of Question by tez-ga on 29 Nov 2002 14:21 PST

This seemed to be Morse code in contrast with just the sound of a
teleprinter -which may still be part of some newshour theme music - I
am pretty sure it contained both long and short beeps.  And while I
watched the News Hour 4 or 5 times a week for many years, I only
encountered this kind of signal 2 or 3 times.

tez-ga,

The answer to your question is that the station is probably doing it's
station call letters for identification as required by the FCC. While
there is some flexibility over the form in which the station
identifies itself and the frequency with which it does it, a PBS
station (such as one showing the "news hour") would probably go above
and beyond to identify itself so as not to put their license into
jeopardy. Broadcasting the callsign in morse code is considered good
practice and dates back to the old days when morse code was a defacto
standard for wireless communication.

Here is a link to information on callsigns and station identification
from the FCC website:
http://www.fcc.gov/cgb/statid.html

And the FCC rules on TV broadcasting:
http://www.fcc.gov/mb/audio/decdoc/public_and_broadcasting.html#ID
Station Identification. Stations must make identification
announcements when they sign on and off for the day. They must also
make the announcements hourly, as close to the hour as possible, at a
natural programming break. TV stations may make these announcements
on- screen or by voice only. Official station identification includes
the station's call letters followed by the community or communities
specified in its license as the station's location. Between the call
letters and its community, the station may insert the name of the
licensee, the station's channel number, and/or its frequency. However,
we do not allow any other insertion.

For the sake of completeness, here is a list of morse code
abbreviations. If you are determined to figure it out, record the TV
then play back the audio over and over until you can get it (they
normally play the callsign at a high speed (>20 words per minute) to
keep it short).
http://www.babbage.demon.co.uk/morseabc.html

(Let me know if you need a hand interpreting it - as well as being a
google researcher I am able to read morse code at about 18wpm - not
sure how that would help in this kind of forum, but I'd be silly if I
didn't mention it!)

Regards calebu2-ga

Search strategy:
From www.fcc.gov : [Station Identification]
and [station identification regulations public television] (all words
required)
From Google : [Morse Code]

Fantastic, thank you for a thorough answer and search strategy!  So
perhaps this is a way for the station to catch up to their schedule
when there's a delay - saving the half-minute that station id.
normally takes by overlaying it with the start of the show.
   And thanks for offer to help decode it - it happens so rarely that
I doubt I'll manage to record it any time soon, but maybe I'll call
the station and ask them exactly what they're broadcasting.