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Some friends and I have discussed setting up a PPP dialup Internet gateway (solely for private use) for fun/nostalgia purposes. I've been reading through the Linux-PPP Howto at TLDP (old, I know, but a good starting point at least), and I came across something that I can't seem to figure out what it is.

In any case, being able to have multiple people dialed in at once will probably require a special service from the phone company which I'm not going to pay for for something that's just for fun, so we'll just do without, but nevertheless I am curious as to what sort of hardware you'd need.

On this page, the HOWTO author refers to a "rotary dialer" as the thing that provides a single number to access a modem pool. I was curious about it, but when I Google "rotary dialer" everything that seems to come up on the first several pages refers to the old rotary telephone dialing interface (or mockups of it for smartphones), which clearly isn't what the HOWTO is talking about.

Again, I have no intention of going so far as to incorporate this, but I am curious--is there another name that the sort of device the HOWTO is referring to is known by?

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  • Actually it says a "rotary dial in set of telephone lines".
    – user253751
    Oct 17, 2018 at 22:02
  • Ugh, I linked the wrong page. Thanks for the catch.
    – Kurt Weber
    Oct 18, 2018 at 17:50
  • "our rotary dialer (this is a single phone number that connects to a bank of modems - the first free modem is then used)" - sounds like it's referring to a single phone number that connects to a bank of modems - the first free modem is then used.
    – user253751
    Oct 18, 2018 at 21:15
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can provide and accept your own answer.
    – Ron Maupin ♦
    Dec 25, 2018 at 9:44

2 Answers 2

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In the 1990s in a British regional ISP, we had a choice from the telephone company of getting two settings for multiple lines:

  • In the ordinary hunt group, the next incoming call would arrive on the lowest unused line on the group
  • In the rotary hunt group, the next incoming call would hunt from the last position for the next unused line of the group

The advantage of the rotary variety was that if there was a failure on say line 2 of 10, it would manifest itself more often in the plain hunt group than the rotary. Some faults would limit you to just the lines below the fault.

Once upon a time these things were mechanical. In the rotary configuration, the "return to first" spring was removed, leaving the rotator where the last call left it.

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From the HOWTO you linked:

rotary dial in set of telephone lines

When I wore a younger man's clothes, back in the late 1990ies, I ran a bunch of Shiva LAN Rovers (in their IBM guise labelled as IBM 8235). In short, they were essentially a 1RU box with a LAN interface (our first ones had Token Ring, of course!) and 8 slots for modems or ISDN BRI adapter cards.

Our PBX guys configured something they called a hunt group across the 10 PSTN and 8 ISDN-BRI "channels" we had. That gave us one number for PSTN access and one for digital/ISDN access, and the incoming call would be dispatched to the next free line or B-Channel. It helped a great lot to keep configuration simple for the remote offices and mobile sales force.

I think that the rotary dialin set is pretty much the same thing, maybe with a slightly different dispatching strategy than a hunt group.

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