-=> Quoting Jonathan de Boyne Pollard to Barry Geller <=-

 JdBP> One thing that concerns me about ISDN is whether or not the modem has
 JdBP> to be powered on all of the time.  This is of most concern when it
 JdBP> comes to making voice calls.  If I went for ISDN, I'd need to be able
 JdBP> to make voice calls at the same time, which I gather can be done using
 JdBP> one of the "B" channels.  True, some ISDN systems have an external
 JdBP> socket for an ordinary voice telephone (Does the USR Courier I-modem
 JdBP> have this, anyone?), but it seems to me that logically the ISDN modem
 JdBP> has to be continuously powered if I want to make voice calls over the
 JdBP> ISDN line. 
 JdBP> The important thing that I'm concerned with is being able to make (and
 JdBP> receive) voice calls at the same time as ordinary data calls.  If, in
 JdBP> order to achieve this, ISDN requires that the PC, or modem, be
 JdBP> continually powered, then it may turn out to be cheaper just to rent a
 JdBP> second voice line instead.   


It almost certainly has to be powered on. But it *doesn't* have to be
"off hook". So the only charges will be the for the (miniscule) amount
of power used by the TA.

--- Blue Wave/DOS v2.30