Jim, in domestic audio equipment I respect your knowledge on the subject,
but for professional communications equipment where the present digital systems
break down to an analog voice channel, 600 ohms is still very much the
standard.
The problem came with working with different countries was that each
authority had its own standards for line levels external to the comms system.
When
the particular company I worked for until retirement two years back migrated
to the now defacto standard of SDH they made a wise decision to change to
analog channel levels of 0dBm, TX/RX at test tone levels. This made life a
whole
lot easier when maintaining the communication systems. It was also now
possible to run data links at a higher level rather than the previously
accepted
figure of -13dB down on test tone which had roots in the old analog microwave
systems channel loading effects.
After saying all this little use is now made of analog voice channels with
most of the links coming through as direct digital links to telephone switches,
WAN and LAN systems and the like in 2Mb increments.
No 600 ohms audio is not dead yet, at least in the professional
communications environment.
Bob, G3VVT
K2 #4168
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