I can tell you one thing for sure, the REX has no effect on the modem.
But you can prove that to yourself by just removing it. It doesn't hurt
anything and it won't even lose it's programming. Just pop it out, and
see that it made no difference.
Have you tested the line with a plain analog telephone?
Have you verified the modem cable doesn't have a broken wire?
Since you are talking about dialing vs answering, is the the ANS-ORIG
switch in the ORIG position? (Answer vs Originate)
Measure the voltage between tip & ring when the the modem is on-hook. It
should be 48vdc
Measure the current on either tip or ring when the modem is off-hook. It
should be about 20ma, at around 9vdc (actually a wide range from 3 to 12)
--
bkw
On 2/3/22 07:04, Cedric Amand wrote:
Hello everyone,
I'm a new member, out of Belgium, I have a dozen of vintages PCs, I
especially likes laptops. I'm an electronics engineer which helpes for
fixing. Thanks for welcoming me and thanks to whoever created this in
the first place.
I'm trying to make the internal modem of my Tandy/RS Model 102 work again.
I've connected it to a small home phone exchange (pabx) so that I have
real proper vintage phone lines , but the same problem occurs on my home
phone line (which is not PSTN anyway, it's an emulated analog line turn
into voip by a modern cable modem router)
I absolutely wanted to have my own "lab" of proper PSTN lines so that's
why I have my little PABX from the 90s; which gives me the possiblity to
experiment with modems.
My problem is ; my model 102 does not pickup the line.
A regular analog phone does, a good old USRobotics Courrier 56K does,
but the T102 does not.
I have the proper Tandy grey/beige(rather pink now) cable
It's inserted in the right way. My init string (STAT) is starting with
M, for internal modem
If I put a phone on the gray line, and "pink" in the PABX ; i can hear
my PABX's dial tone, until I make the M102 dial, in which case the phone
goes silent (which is normal).
But the PABX doesnt show the line as beeing picked up (a led should turn
red), I can hear the M102 pulse dialing "in the void", but to no end...
The PABX supports pulse dial. I tried 10pps and 20pps.
But it seems the problem is not dialing, it's the actual, i'd say
"electrical" pickup of the line.
It seems either the voltages are not right, or something is not working
like it should.
I tried BASIC with "CALL 21200" (which pickups the lines) you can hear
the relay click, but again, the PABX does not see that as someone
picking up a phone.
I have an European M102 (could that be an issue ?) My "phone line"
(vintage PABX) is a european (belgian) one.
However the M102 has been "upgraded" by a REX# v2.0 rom by the previous
owner, that may be an issue (this upgrade was not my doing. I can barely
use REX.) I'm with TSDOS101
It's unclear if, eventually, the modem section could need a repair
(recap or smth)
Another possilbity would be that the tone i'm giving it (440Hz over
here) is not recognized (seems to be 600Hz in the US), but I find this
unlikely this would be software controlled, and my M102 is a Belgian
model it even has the "RTT" (telco of the time) sticker on it
I'm out of ideas.
Any help greatly appreciated
--
bkw
