I've been up to no good this afternoon with a pair of VIC-20s. A very long time ago, I asserted that you could connect some modems with just a length of line cord in the middle. In the time since then, various folks have done things to recreate the old days of dialup BBSes and even ISPs, and they've gone to lengths to have a line simulator in the middle, or a battery, or other strange things.
This always bothered me since I clearly remembered running a cord down the hallway between my little Commodore and the family's "big machine" (386) and plugging it into both modems. I did "ATA" on one, then ran to the other one and did "ATD", and they connected. Then I had a very slow, very crappy text-only "network" between two very dissimilar machines... without having a second phone line in the house!
That's where I've been for the past 30 or so years, but today I got a chance to finally figure this one out. I've been slowly accumulating the pieces of the puzzle, and recently, the last one landed. I got one of these "Penultimate+2" cartridges for the VIC which has a "dead test" in it. My original machine from the early 80s hasn't booted into the usual BASIC screen for years, and I wanted to know why.
Finally, this cartridge told me today: it's a bad BASIC ROM. Well then. That makes some amount of sense why it can't get to the usual "CBM BASIC V2" blahblah, and why other things (like certain carts) will still work.
Then, while pondering what to do about the bad ROM, I noticed this Penultimate cart had a built-in terminal program. Would it talk to the modem without using BASIC? Only one way to find out. I had a couple of old modems from various fits of boredom over the years, plugged one in, and gave it the good old "AT" to see if it lived. It DID: "OK".
Well, obviously now it was ON. I had to break out the "good" VIC-20 a friend gave me in the 90s to get it set up with the second modem. Since there's only the one cart and it can't be in two places at once, I instead typed in a godawful program to sling bytes between the modem, keyboard and screen. Once that was working, I tried the "AT" there, and that modem also worked: "OK".
The next thing was clear: hook them to each other and connect them. One small problem: I needed a phone cord. I haven't had a regular old analog phone for well over a decade now, and even that was late in the game to get rid of them. Where the hell was I going to find a plain old flat satin phone cable?
Well, somehow I found one buried in a box of nerd stuff, and naturally one of the retention clips snapped off, so I had to curl it around and jam it in there just so to keep it connected. Then it was a matter of ATD on the one and ATA on the other and I was rewarded with a terrible racket and then CONNECT.
I only have a single working RF modulator (and TV for that matter) so I could only watch this from one side of things, but it was still a great feeling just being able to dance around on the keys on one end and see it appear on the one that was driving the display.
So, yes, I can now (again) positively assert that at least when the Commodore 1670 is involved, you can totally smack it around and make it drive an otherwise dead pair that goes straight into another modem - no telco, no battery, no dial tone, etc. (You might need to do ATX1 to make it not look for the dial tone, naturally.)
I sure hope that isn't useful information to anyone. For me, it was more about putting to rest this random nagging thing in the back of my head. Other people also worry about making sure they're not handing out misleading info as authoritative, right?
Side note: yes, these modems make a "pa-tink, pa-tink, pa-tink" noise after the dial phase (if any) while waiting to connect. I have no idea what this clicking noise was for in this old modem. Maybe someone out there knows why and will send me a comment. Hint hint.
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