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PC Modems Used With A Mac

Posted on 1997-12-28
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Last Modified: 2013-12-27
I'm trying to use a PC-version USR Sportster 28,800 Fax/Modem on a Mac 7200/75. I can't seem to get it to work above 9600 BPS. I've tried changing the default DIP switches by turning 1 off also, and I've tried several INIT strings, but to no avail. Is there a different INIT string or DIP switch combination I should be using, or do I need to use FreePPP (which I haven't been able to locate) instead of the ConfigPPP Control Panel I've been using? Or is using this PC modem with my Mac a lost cause?
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Question by:s122897
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Expert Comment

by:kcowan
ID: 1542423
The cable you are using probably does not support hardware handshaking. You will need a Hardware Handshaking cable (aka Mac to High Speed modem.) This cable has the DSR and DTR pins connected. Without the hardware handshaking, the modem will top out at about 9600 baud.
I have used Zoom, USR and Motorola modems designed for PCs on a PowerBook with no problems. The only difference I have seen between most PC and Mac modems is the Software included.
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Author Comment

by:s122897
ID: 1542424
I tried switching cables with one provided by a friend who's proficient with Macs. Unfortunately, the cable change produced the same results as before. My friend assures me it's the right cable, and a good brand (ResNova). Even though it didn't seem to work in my case, kcowan's proposed answer was an excellent trouble-shooting guess, according to my friend.
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Accepted Solution

by:
rifty earned 100 total points
ID: 1542425
The PC modem can be used with a Mac, no problem. It's almost certainly a sofware or configuration problem. Return the dip switches to the default setting - whatever they were that worked on the PC.

A copy of FreePPP is available by going to

http://www.telstra.com.au/cgi-bin/vsl-front/

Search the Mac archive for the word freeppp and it will provide you with a suitable download site (I just tried it!)

Install FreePPP and configure it to run at, say 19200 baud, and see how that goes. Use AT&F0 for the init string.  

Add a comment here if you don't know what other settings to use, but if you can get it to run at 9600 already, then they should be right. FreePPP installed should actually use those already established settings.

FreePPP is a good system to use with a modem that doesn't seem to be working properly with others. If you don't like it, you can easily go back to what you had.

Good luck!

Rifty.
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Expert Comment

by:birchallr
ID: 1542426
Hello,

Use AT&F1 for the init string.  That's it!

Use the factory standard DIP switch settings (as printed on the bottom of the modem), except for DIP switch 1 in the DOWN (ON) position to force the DTR signal high.

Also make sure that your modem cable is a new one, good for "hardware handshaking" or was labeled as "high speed modem cable".  Older Mac modem cables are different and will give you errors with 14.4 or 28.8 modems.

Has your friend confirmed that the cable is correct, by running it with a 28.8 or higher modem?

Set your PPP software to "hardware handshaking" (RTS/CTS) and your serial port speed to 57600 bps or higher.

Regards,

Richard
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Expert Comment

by:rifty
ID: 1542427
s - if you find that Richard's comment solves the problem rather than anything I've said in my answer, then feel free to reject mine and invite him to submit it as an answer. I don't mind as long as you get things working to your satisfaction!

Rifty
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