> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On
Behalf
> Of Mark E. Skeels
> Sent: Thursday, August 16, 2007 9:10 AM
> 
> Here's another question:
> 
> Does a DSL modem take the phone line "off hook?" (I doubt it..)

Your doubts are correct.  A DSL modem does not take the line off hook.
 
> Or does it simply communicate over the phone line, at high frequency,
> with no regard for hook status or dial tone?

That's right.  A regular telephone uses 0-4KHz and on/off hook signaling
(some use ground start too).  ADSL uses 20KHz to ~1.2MHz.  It's likely
the upper limit has been pushed higher now by ADSL+ and ADSL2, as I
stated before, I've been out of the field for a few years now.

-Mike

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