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Table Of Contents  CertiGuide to A+ (Core Hardware)
 9  Chapter 0111:  Peripheral Devices
      9  VII  Modems

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S-Registers

Like all other intelligent devices for PCs, the BIOS in the modem can be configured differently from the factory defaults. These settings are known as the S-Registers. Suppose your PBX at the office could get an outside line in less than one second. By changing the value of Register S8, you control the amount of time a comma pauses. Modems may have dozens or even hundreds of S-register settings.

[spacer]The Hayes Modem

Denny Hayes and Dale Heatherington started making modems in 1978. Hayes Corporation was quite profitable for a long run. Competitors came out, effectively cloning the Hayes modem. The Hayes Corporation filed lawsuits to protect the AT command set, and lost. In an effort to stem the losses, (without ruining the profitability of Hayes SmartModems), the firm released less expensive modems under the names such as Practical Peripherals, and Cardinal, to name a few.

In April of 1999, Hayes Corporation as a stand-alone entity ceased to exist when Zoom Telephonics bought out "most of the modem assets" owned by Hayes.


The original Hayes modems were external devices that used a transformer for power, a phone line that connected with an RJ-11 jack and a DB-25 serial connection to the PC. They were enclosed in an aluminum case (to help dump all the heat they made). Later, as more of the discrete components were shrunk, the modem didn't need as much power, and was able to be put inside the PC as an expansion card. These are known as internal modems.


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AT Command Set
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Compression and Errors
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