[TowerTalk] RE: TowerTalk Digest, Vol 19, Issue 119

[Dudley Chapman]

Jim,
    The term "600 ohm line" doesn't refer to the impedance of the line
itself.  In old audio systems where all the lines were balanced, the input
and output impedances of amplifiers and mixers were 600 ohms.  The balanced
line and he low impedance helped keep noise pickup down, especially in long
runs of audio cable.  

    I don't know if the phone company uses 600 ohm equipment or that
terminology, but it's a common expression among broadcast engineers when
referring to the balanced audio lines.

<snip>
I'm a fairly old guy, and I have never seen a transmission line having a Zo
much greater than about 150 ohms that wasn't some form of either ladder line
or open wire line. 
</snip>

Dudley - WA1X