["Followup-To:" header set to sci.electronics.basics.]
On 2005-10-19, wrote:

Jasen Betts wrote:
On 2005-10-18, wrote:
the relay (soldered) has approx 20kohms between the coil and 200k
between the output, when dis/reconnecting the dialtone returns but then
again goes busy by itself!

That first figure sounds way too high, 200 ohms would be the low side of
believable can you check again?

seing as it doesn't look like a short

also can you measure the current through the modem when it's connected to the
phone line (but on hook/powered off) a ohm meter running at 1.5-9V soetimes
sees things differently to the phone line (48V on-hook)

Is it possible you've measured the ring detector and not the relay?


took the modem out of the pc, relay in:0.5kohms both ways (the flyback
diode seems to be out but not sure if it can be tested without
desoldering) and out:approx 500k ;

That sounds much better.

when I plug in the line the modem goes offhook but not right away and
the relay output closes.

ooh... you hear the relay closing? that doesn't sound like a relay fault.

sounds line a fault elsewhere

caa you use a terminal program to "talk to" the modem
if so run all the tests.
at&t1
at&t2

etc...

see how it responds to commands like

ath (go on hook)
ath1 (go off hook)
atxdp9 (dial nine pulses)

both with the modem connected to to the phone line and disconnected.

There is a diode bridge but cannot really tell if the
relay is on the host side though it is rated 0.5A 20V/0.1A 100V;

could the bridge be for the modems power supply?

at 20V rating it'll be atleast half switched by the modem.
otherwise behing it

MOV is open at all times,
How do I test OC and can I pull it out if I do
not expect any calls?

huh?

Bye.
Jasen