HP 600 Series, Services And Applications

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Manual Adapter
A manual adapter refers to any DCE (ISDN terminal adapter, modem, or
DSU/CSU) that will initiate a connection to a remote DCE when the router
raises the DTR lead (the data-terminal-ready signal) on the interface to the
DCE. This is simply hardware-level signaling to initiate and break
connections. Any of the synchronous interfaces (RS-232/V.24/V.28, V.35,
RS-449/422/V.36, and X.21) may be used to connect to a manual adapter.
Connections with a manual adapter may be initiated in one of two ways:
When data is available
When the circuit is enabled
There are four combinations of parameter settings to initiate connections.
That is because there are two routers involved in setting up a switched
connection, and there are two connection initiation methods on each router.
Table 3 shows the four possible combinations. Of the four combinations,
only the two shaded combinations are recommended. Thus, one side opens
the circuit when data is available and the other side always waits to receive
data.
Table 3. Parameter Combinations for Initiating Manual Adapter Connections
Side A Router Side B Router
Circuit is enabled Circuit is enabled
Circuit is enabled Data is available
Data is available Circuit is enabled
Data is available Data is available
When the Connection Initiation parameter is set to “circuit is enabled” on
both sides, the circuit will never hang up. The user will incur charges for a
permanently open circuit!
When the Connection Initiation parameter is set to “data is available”
on both sides, the circuit will never get established! HP routers do not
implement the physical “ring indicator” signal, so there is no way to know
about the arrival of an incoming call.
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Improving Network Availability
Switched Circuit Types
3-17