IBM PCjr. Modem - What can I do with it?

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IBM PCjr. Modem - What can I do with it?

Postby GHiero » Sun Feb 09, 2014 7:54 pm

My PCjr. has the IBM Modem inside it, and while it helps with the COM port assignment and passes the diagnostic check, I have no idea how to use it since it is not Hayes compatible. Will a terminal emulator program like Telix work so I can dial into a BBS?
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Re: IBM PCjr. Modem - What can I do with it?

Postby Brutman » Sun Feb 09, 2014 9:04 pm

Novation made the modem so Novation specific commands will work on it. The full set of commands for the modem can be found in the technical reference manual.
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Re: IBM PCjr. Modem - What can I do with it?

Postby GHiero » Mon Feb 10, 2014 9:01 pm

Can you suggest a telecommunications program I can use? Telix 3.51 doesn't respond to the PCjr.'s keyboard. I don't think the telnet client in mTCP supports modem dial up.

I understand that Cartridge BASIC has a terminal emulator that is run with the command TERM. Would that be sufficient to dial into a BBS?
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Re: IBM PCjr. Modem - What can I do with it?

Postby Brutman » Tue Feb 11, 2014 8:55 am

"TERM" is sufficient except it is so slow - interpreted BASIC at its best.

You need to find an old terminal emulator program like Procomm or Telix. The old ones do not assume Hayes compatibility and let you program them with the commands specific to a modem. I assume you found the technical reference and have the commands ready?

And remember, it's 300 bps. This is going to be painful.
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Re: IBM PCjr. Modem - What can I do with it?

Postby geoffdaddy » Tue Feb 11, 2014 1:40 pm

Seems like the best use for the modem would be to bypass the modem chipset, deadbug some RS-232 drivers on the card and use the UART on the card to build out a second serial port.
PCjr: 10MB RACore 01 hard drive expansion, Hotshot 640kB RAM expander, optical mouse, Xircom PE3, speech sidecar.
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Re: IBM PCjr. Modem - What can I do with it?

Postby GHiero » Tue Feb 11, 2014 9:20 pm

I am really only doing this as a proof-of-concept to prove (to myself) that I have some control over every peripheral in the system. The IBM PCjr. Modem is the last part of my system that I have yet to make it do something useful.

So I started the TERM terminal emulator. I keep all the settings at their default. The basic command is DIAL, and goes like this :

DIAL 12345678900

Next I press f1, which seems to execute the command, and I get :

BUSY
OK

Using the query command, Q, I get
H0S8BT0

Sometimes the B is not present (busy), but anything I try to call out to I get a busy.

I have used two other modems successfully over this line within the past year, with is a Comcast line, presumably VoIP based. They were Hayes compatible modems, but one was a 56K modem and the other a 1200 baud modem.
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Re: IBM PCjr. Modem - What can I do with it?

Postby Brutman » Tue Feb 11, 2014 11:53 pm

Can you hear it dialing? How long did it take for it to respond with "BUSY" ?

If it is immediate it might be confused about the sound of the dial tone you are getting. (I know that Hayes modems could be told to ignore the dial tone and just blind dial.)
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Re: IBM PCjr. Modem - What can I do with it?

Postby GHiero » Wed Feb 12, 2014 9:22 am

It happens pretty quickly, takes a bit longer if I set the call command to a high number. The weird thing is that this Modem does not have a speaker built into it. There is no tweeter anywhere on the board, and it doesn't make the PC speaker tweet either.

Edit 1 : Since I am using the house line, it gives a stuttering dial tone for the first two seconds. This indicates I have unread voicemail messages. I usually don't check the voicemail since I only use the house line as a fax line. I cleared the voicemail and now the phone gives a clear dial tone. Perhaps the stuttering was confusing the modem as it is similar to a busy signal.

Edit 2 : No "perhaps about it", that was the problem. I cleared the voicemail, waited for some time for the stuttering to go away and was finally able to get the modem to dial out, no BUSY. Now to actually connect to something...

Edit 3 : When I tried dialing, I could very faintly hear the sounds of what I recall to be pulse dialing. I believe the Tech Reference says that the default is tone dialing. I put a w in the dial command and dialed the number for the Prison Board BBS. The dial command looks like this :

dial w19723290781

The w guarantees that tone dialing will be used, otherwise I got a busy signal. When did this, it connected to the Prison Board BBS, but stated that the minimum connect speed was 300 and disconnected :( My modem is connected to 300bps but is using a 7-bit data format. Let me try it with 8-bit.

Edit 4 : I set the data rate to 8-bit, but at 8-bit the modem cannot use parity. This causes garbage characters to show up on the status screen where the program should echo what the modem is doing. It still connected to the Prison Board BBS, but the BBS still complained of the minimum rate and disconnected. I tried another BBS, but it complained that I was using 7-E-1 settings even though I was using 8-N-1 settings. A third BBS disconnected after I tried to login as a guest, a fourth BBS complained that it need a 2400 minimum connection and hung up, and a fifth just connected and disconnected without displaying anything.

Having gone through five of the twenty five known public BBSes that still allow for dial up access, I can only conclude that a combination of several factors prevents this modem from working with modern BBSes. FIrst, the software I am using is inadequate, especially its 64KB limit and lack of ANSI support. Second, the line quality of the modern VoIP telephone line is causing a greater amount of corrupt data than a Plain Old Telephone System using copper wire throughout. This has effected other modems I have used. Fourth, the modem is just too slow to connect reliably to many, if not most modern BBSes.
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Re: IBM PCjr. Modem - What can I do with it?

Postby geoffdaddy » Thu Feb 13, 2014 2:39 pm

GHiero wrote:Edit 4 : I set the data rate to 8-bit, but at 8-bit the modem cannot use parity. This causes garbage characters to show up on the status screen where the program should echo what the modem is doing. It still connected to the Prison Board BBS, but the BBS still complained of the minimum rate and disconnected. I tried another BBS, but it complained that I was using 7-E-1 settings even though I was using 8-N-1 settings. A third BBS disconnected after I tried to login as a guest, a fourth BBS complained that it need a 2400 minimum connection and hung up, and a fifth just connected and disconnected without displaying anything.


You should be set to 8-N-1 to talk to any BBS. I suppose that the reason it's reporting your settings incorrectly is because you are using a terminal program that either: A. has no VT100 emulation, or B. has crappy VT100 emulation... one of the escape code sequences returns the settings of the terminal data bit length, parity and number of stop bits.
PCjr: 10MB RACore 01 hard drive expansion, Hotshot 640kB RAM expander, optical mouse, Xircom PE3, speech sidecar.
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Re: IBM PCjr. Modem - What can I do with it?

Postby geoffdaddy » Thu Feb 13, 2014 2:44 pm

I have used 300bps over a cell phone call before, so I imagine if you're using any properly classified/shaped VoIP service through a carrier class network then it should be more than adequate for 300 bps.

I suppose it's also possible that whatever system's modem you are connecting to has crappy support for Bell 103 compatibility since it's mostly vestigial support at this point, or that the PCjr's modem really is That Bad. ;)

FWIW, back in the day a friend of mine had a Tandy 1000EX and bought the internal PLUS card 1200 bps modem for it. Almost NO BBS (or Telenet/Tymnet/Sprintnet for that matter) supported 1200bps mode correctly and/or the firmware on the modem was too persnickety to work, so he was relegated to connect at 300 bps most of the time.
PCjr: 10MB RACore 01 hard drive expansion, Hotshot 640kB RAM expander, optical mouse, Xircom PE3, speech sidecar.
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