Question about modems

Electronics Plus sales at
Wed Nov 13 19:22:38 CST 2019

-----Original Message-----
From: cctalk [mailto:cctalk-bounces at] On Behalf Of Fred Cisin
via cctalk
Sent: Wednesday, November 13, 2019 7:08 PM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: RE: Question about modems

On Wed, 13 Nov 2019, Electronics Plus via cctalk wrote:
> And here my problem is that I have the old modems, but I can't test them 
> because I no longer have a land line. Is there any way to test an 
> internal or external modem without anything except broadband or cellular 
> connections? I know I can't test the acoustic modems, but I was hoping 
> to be able to test internal ISA and PCI, as well as external modems from 
> 300 baud to 56k. Perhaps there is some inexpensive gizmo available?

A "telephone line simulator".
In some cases, you might be able to just connect them, with a power 
One set to "Originate" and one to "Answer", of course.
But, you also want a "dial tone".
And, if you want to test answering capabilities, then you also need a 
"ring simulator", which is 90VAC at 20Hz.  (often a lot of tolerance)

What do you need to do to use an acoustic modem with a cellphone?
You can get a "retro" handset for a cellphone, that will fit the rubber 
cups, but, will it work?

A young gent (about 22 yrs old) reminded me of HyperTerminal on XP. Since I
have stacks of old working XP laptops, I can simply connect 2 modems to each
other via a POTS phone cable, attach each modem via serial cable to a
different laptop, and set one to Listen and the other to Answer via
HyperTerminal. If I want to transfer files, I could use PuTTy, which also
runs on XP. Seems like that should take care of both send and receive on
both modems? Now to make a simple batch file that can automate the process,
since I don't want to do everything manually for 50+ modems!

I only have 2 acoustic modems, so I will set them aside for now. I used to
have a "telephone tester" machine from Radio Shack, but it disappeared many
years ago. I do have an old TAB book of "telephone projects" and another for
test equipment that I could build, but that would be a lot of trouble to
only test about 50 items.


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