Chapter 5: Configuration
TRANSPARENT 2 X CLEAR CHANNEL PROTOCOL
Due to the large number of existing videoconferencing circuits that utilize dual-port terminal adapters or two SW56 DSU/CSU units, the ISU 512 has been designed to operate with these existing circuits by using a transparent 2x56/64 Clear Channel protocol. During incoming and outgoing calls, the ISU 512 attempts BONDING mode 1 protocol first. If the BONDING protocol fails to negotiate with a far-end unit supporting the BONDING protocol, the ISU 512 automatically attempts 2 x Clear Channel protocol. During this mode, the first connected call (incoming or outgoing) is attached to the primary port (V.35 connector) and 56 kbps or 64 kbps data rate is used depending on the Call Type used during the call placement or acceptance. Front panel display reads 1x56/64. The second call, (answered or initiated) is attached to the RS- 530 port (an RS-530 to V.35 cable adapter, part number 1200072L1 is available) and reads 2x56/64.
The second call is dialed using the front panel, the VT 100 terminal interface, or by using the RS-366 port. By using an RS-366 Y cable adapter (part number 1200120L1), the single RS-366 port on the back of the ISU 512 can be converted to two ports. The RS-366 Y cable connects to the single RS-366 port on one end and has two connectors for the dual ports required on videoconferencing equipment. The cable should be enabled from the front panel interface or through the VT 100 menu screen. The cable has one connector labeled PRI- MARY. This primary connector places the call for the primary port, the V.35 connector. The other RS-366 connector is used to dial the RS-530 port. A call must currently be active on the primary port before the second call can be placed. This ensures the first call does not connect with a unit supporting the BONDING protocol. For example, if a call is placed through the primary RS- 366 connector, and the ISU 512 connects to a unit on the other end that sup- ports the BONDING protocol, then BONDING places the remaining calls au- tomatically. If the ISU 512 does not find a unit at the other end that supports BONDING, the ISU 512 keeps the first call active, and automatically uses 2 x Clear Channel Protocol. The second call placed through the secondary RS-366 connector connects on the RS-530 port.
If the ISU 512 is to be used in the application described, then the RS-366 Y cable should be enabled and the connector type for the DTE port should be set to the primary port, the V.35 port. An RS-530 to V.35 cable adapter (part number 1200072L1) can be used to adapt the RS-530 port to an existing V.35 interface when required.
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