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Franc Zabkar wrote:

On Tue, 20 Jun 2006 00:48:22 +0100, Pooh Bear
put finger to keyboard and
composed:

Franc Zabkar wrote:

On 19 Jun 2006 08:44:34 -0700, put finger to
keyboard and composed:

Looked at several Motorola SM56 modems an all have the same fault-non
infinite resistance at line jack which causes them to take over the
line once the line is plugged, so none of the telephones can be used!
Checked the MOV and it is ok and there is no relay on modem !(at least
not a box type, just few too many smd transistors doing smth?)

There is a diode bridge so the line interface is a 'dry transformer'
type.

If there is a transformer, then the DAA is probably dry, as you say.
Otherwise there would usually be two chips, one on the line side and
one on the host side, with two or three ceramic caps providing the
isolation.

The one I have has no relay or transformer.

I'm seeing 19M across the line on the bare pcb.

You might be looking into a diode bridge, either discrete or internal
to a line side chip.

There's a WO series 1 amp bridge on the line.

I'd be checking whether the modem goes off-hook when the PC is powered
down. If not, then your line side electronics is probably OK. Next I
would check whether the modem grabs the line during the POST, ie
before its drivers have a chance to load.

I'll check that when I get a sec.

Graham