Chapter 1: Understanding ISDN and the ISU 512
Dialing from the ISU 512 is accomplished in a variety of ways:
•Manually from the front panel keypad.
•Manually from up to ten stored numbers.
•Automatically through an RS-366 dialing port used in video conferencing applications; a special RS-366 Y cable provides the two RS-366 interfaces for this application (part number 1200120L1).
•V.25 bis in-band dialing (used in applications such as LAN/WAN bridg- ing).
•Dialing while DTR is enabled. From Stored Number 0.
•Dialing from the VT 100 terminal interface.
The ISU 512 (U interface) also supports dedicated leased 2B1Q services. This provides a dedicated point-to-point service (as in a limited distance modem or leased line application) with no dialing necessary.
The ISU 512 is designed to operate in a dual-port mode for videoconferencing at 112/128 kbps. This allows end-to-end compatibility when communicating with a video system that is utilizing two Switched 56 DSUs or a dual-port ISDN terminal adaptor. For this application, 56/64 kbps is transmitted over the V.35 interface and the RS-530 interface. An RS-530 to V.35 adapter (part number 1200072L1) is available to provide the necessary V.35 interface for the second port. Also, a special RS-366 Y cable (part number 1200120L1) provides the two RS-366 interfaces for this application. For convenience in communi- cating with multiple video sites, the ISU 512 transparently switches between the dual-port mode at 112/128 kbps and the single-port mode of 336/384 kbps without user intervention and reconfiguration of the unit.
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