Sunday, May 31, 2009

1964 Livermore Data Systems Model A modem - followup

Alright, here's some photos of the beast:

And, in no particular order, some answers to the questions I've received:

1. This modem uses Bell 103A modulation, in "Originate Mode" only. Unfortunately, that means you probably couldn't have two Livermore Data Systems Model A modems talk to each other. The "Model C" seems to be the first one that also supported "Answer Mode" modulation.

2. This modem is solid state; it uses transistors (albeit early, metal canister ones.) It doesn't have vacuum tubes in it. (Whew!) It functions exactly as I received it twenty years ago - I haven't modified or repaired it in any way. Yes, I am as amazed as you are! :-)

3. The host used in the video, as well as all the accounts, credentials, &etc, were set up in my lab specifically for testing the modem and were taken down the next day. Hence, I didn't have to worry about obscuring my typing or login credentials, &etc. Thank you to all the concerned people out there who warned me that someone might be able to deduce what I was typing.

4. We didn't do PPP or SLIP across dial-up modems prior to 9600 baud because the protocol overhead would saturate the line. In my mind, it doesn't matter at which point in the communications path each layer of the OSI model gets peeled back, the data from the host still made it to the client. Dialing in to terminal servers (or directly into UNIX boxes or mainframes) is how "we did it back then." I did subsequently get a very relaxed-protocol PPP connection to work through the modem, but it barely functioned. 56-byte pings took between 3000 and 5000 ms. DNS saturated the lines. TCP connections failed (handshake timeout) most of the time due to the latency. A browser simply wouldn't load a page.

5. Yes, that's a beer on the table behind the counter. Specifically, it's a home-brewed clone of Sweetwater 420 IPA. If you like IPAs, Sweetwater makes a darned tasty one. ;)

Thanks for all the comments, feedback, tweets, emails, &etc! I found the modem inspiring, and hoped others would too. More to come! My gmail address is also phreakmonkey

- K.C.
aka phreakmonkey

Thursday, May 28, 2009

Circa 1964 Livermore Data Systems Model A Modem

So I was going through some old stuff in my garage and I found this antique modem that I've had since I was a teenager.  Turns out it's a Livermore Data Systems "Model A".   I decided to hook it up and see if it works, and I made a YouTube video in the process:

I'll get around to posting some better photos of it this weekend, I promise!