Protocol Analyzer Remembered

Anyone will tell you that as hard as it is to create a working system, the real trick is making two systems talk to each other, especially if you created only one or none of them. That’s why tools that let you listen in on two systems talking are especially valuable.

If you were a well-funded lab back in the RS232 days, you might have an HP4957A protocol analyzer. The good news is that if you still use RS232, these kinds of things are now cheap on the surplus market. [IMSAI Guy] got one of these decidedly cool devices and shows it to us in the video below.

The look of these was pretty neat for their time—a folded-up instrument with a cute keyboard and a CRT-100. You can load different interpreters from ROM to RAM, such as the VT-100, which is essentially an application for the device. Of course, now you could rig one of these up in a few minutes with a PC or even a Pi Pico. But it wouldn’t have the same charm, we are sure you would agree.

You can find a lot of old RS232 gear around, from breakout boxes to advanced sniffers like this one. Too bad we couldn’t afford them when we really needed them.

This could be handy if you have a lot of ports. Either real or virtual. Or, do it yourself.

22 thoughts on “Protocol Analyzer Remembered

      1. I guess they’re pretty simple to make by todays standards but if they’re still on sale, they’re still very relevant I guess? probably industrial equipment/machines.

    1. Perfect to give you cancer from CRT radiation (test & measuring equipment was exempt from lead glass requirement for TV CRTs introduced in early 1950s).

      I’ll take modern LCD devices any time of day.

      1. There must be some data showing how many people went on to develop cancer from CRT radiation from test & measuring equipment to support your bold claim. Could you provide it please? Otherwise, the exemption was probably granted due to the risk being negligible, as the displays are small, and test and measurement engineers generally use this equipment only from time to time, unlike TV and office displays which are larger and used continuously for several hours every day. Furthermore, test and measurement equipment manufacturers may have used leaded glass despite there being an exemption in place, or may have shielded the tube in some other way. But, thank you for your concern.

      2. I don’t miss CRTs either, but I wouldn’t be particularly worried about the ones in equipment like this, nor are they likely to be worse than any other “modern” CRT.

        The 4957A uses the same sort of off-the-shelf monochrome 4:3 CRT that was common in computers and other equipment of the 80’s and early 90’s. Those were all subject to the same ionizing radiation exposure restrictions as TVs, at least in the US.

    1. I bought quite a few of the datascopes for our company, and also a 2 station 64000 system. I remember the HP tech frequently saying (re the 64000) “I don’t know what you guys are doing, but none of our other customers complains about having those
      symptoms!”.

  1. I remember trying to develop a bisync emulation for connecting a cash register to a non-IBM system in the 80’s. We had access to either an HP or a Tektronics protocol analyser but it was just on loan – we couldn’t afford to buy one on our miniscule budget. It was very useful , whatever brand it was.

  2. Back in the 80’s I used to work in the production computing department of a local newspaper. One Monday we came in and wire service was down (Local Reuters node across the corridor to Microbee PCs used as character encoding translators then to Pr1me serial IO cards).
    The techs were tearing their hair out because their HP 4957 said the lines were completely dead but we were seeing wire service messages with abut 50% of the characters garbled.
    Turns out Reuters had been doing some service to their node on Sunday and their tech had plugged our hard wired links into the TTY contact block rather than the RS232 block. Our cheap gear was just about coping with the +/- 50V but the HP was protecting its inputs from the overvoltage conditions.

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