IBM System/7 Functional Characteristics - All about the IBM 1130 ...

IBM COMMUNICATION LINE ADAPTERSThe ACCA can communicate with a host processor over private lines, leased common-carrierfacilities, or switched voice-grade common-carrier lines.The various line adapters that can be installed in the ACCA are shown below.IBM Line AdaptersType Rate (bits/sec) Line Type Maximum Line Length2B limited distance 600 maximum 2-wire 8.25 mileslA leased line 600 maximum 2-wire No limit1B leased line 600 maximum 4-wire No limitIBM World Trade ModemsType Rate (bits/sec) Line Type Type of ServiceIBM 3976-I 200 maximum 2- or 4-wire Private or leasedIBM 3976-11 200 maximum 2-wire SwitchedIBM 3976-111 1200 maximum* 2- or 4-wire Private or leased*System/7 supports 600 bps maximumIn conformance with Electronic Industries Association (EIA) Standard RS232C withinthe United States, and Consultive Committee on International Telephone and Telegraph(CCITT) V24 Standards outside the United States, an attachment option provides thefollowing eight interface signals for non-IBM modems:1. Transmitted data2. Received data3. Request to send4. Clear to send5. Data terminal ready6. Data set ready7. Protective ground8. Signal groundSome modems disconnect when the data terminal ready signal is deactivated in the ACCA.This signal can be deactivated for 1 second by a prepare I/O command that prevents interruptionrequests, provided interruption requests were already permitted by a priorprepare I/O command. At the end of the 1-second interval, the data terminal ready signalagain becomes active, but interruption requests are permitted again only if another prepareI/O command has done so. During the one-second time period, the System/7 isunavailable to any processor that may be attempting to communicate with it. Thedata terminal ready signal is not affected by a system reset.Asynchronous Communications Control Attachment 7-3