Modem and printer cable info for old Macs - Copyright Mar 20 2003 HRJ updated 5/30/05
See my Mac modems section for the modems I have available. See my printers page for printers. All my Mac stuff is linked to from my Mac home page. A Web link to my home page is at the end of this document. Modems Modems are devices that connect your Mac to the Internet via phone lines. I have some older modems that will be adequate for some of my Mac clients. They are connected externally to your Mac at the modem port, you will need a cable for these. While these are slower than the external 56K modems now available, they are a lot cheaper! And for email and occasional Internet use, they may be adequate. Also, older compact Macs like the Plus, SE and so on will only support continuous speeds of 9600 or 19,200 baud anyway: a faster modem will not provide faster Internet access.
For information on how to connect your Mac to networks or the Internet, please look over my list of Mac Web site pointers to find those Web sites which support these kinds of applications. I simply cannot offer recommendations or tell you what you "should" buy, that is a conflict of interest for me as a seller. These sites are not selling anything, they are free to offer their advice and opinions.
The non-Apple modems use the Hayes compatible command set. Many Mac telecommunications and Internet programs allow the use of these kinds of modems. Consult your programs to see if these would be compatible. If I have docs for these modems I will provide them. At these prices I can't provide support or technical info; but they are tested for operation by dialing out and running a terminal session. Most of them are low flat boxes about the size of a paperback book, with a "wall wart" power supply. A few are smaller.
Late model external modems from US Robotics are pretty common. The modem has a set of switches that must be set for proper operation. The settings that seem to work well are below, but your software's needs and modem may vary. 1 down (DTR override) 2 up (Verbal result codes) 3 down (display results) 4 up (echo offline commands) 5 down (no auto answer) 6 up (carrier detect normal) 7 up (load NVRAM defaults) 8 down (smart mode) Most non-Apple modems will require a DB-25 to Mac DIN-8 modem cable. My Web page on available modems offers these cables. Most of the modems made for the IBM-PC market use a DB-25 connector. Most Macs use a DIN-8 connector; (the very oldest 128K and 512K Macs use a DB-9). So you need a cable to fit your Mac's modem connection to the DB-25 connector on the modem. The way the cable is wired for use with a modem and its DB-25 connector, to your Mac's DIN-8 connector, is as follows: DB-25 2 3 4 5 7 20 DIN-8 5 3 2 1 4&6 2 all other pins are not connected. Printers The original Apple Apple Imagewriter I printer used a DB-25 connector, cabled to the Mac 128K, 512K computer with its DB-9 connector; or to a DIN-8 on later Macs. Here's how an Apple cable, model 590-0555-A, is wired between the DB-25 for the Imagewriter I, and the DIN-8 for the Apple printer connection: DB-25 2 3 6 7 8 20 DIN-8 3 5 2 4&6 2 1 To use a MODEM-CONFIGURED DB-25 to DIN-8 cable for an Imagewriter I, you need to connect between the printer's DB-25 and the cable's DB-25, a device called a null modem. This is a device that reverses some of the lines between the cable and the printer. If you compare the modem cable's connections and the printer cable's connections, you will see that some are reversed. Computer to computer, or other devices If you want to connect your Mac's serial port to another computer or to some other device, you'd need to consider how their serial lines are connected. In general, communications between serial devices (like old printers and most modems) are divided between "transmit" signals from the Mac, and "recieve" signals to the Mac. Sometimes those are wired "backward" so a null modem rewires them "backward" again to create the proper connections. This note is too short to detail the signals on a Mac, a modem and on a printer. Consult documentation and other sources for that information. Herb Johnson my Mac Home page