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NT7D16 Data Access card Page 437 of 894
Circuit Card Description and Installation
• The equipment can monitor the DTR lead (optional, depending on the
mode selected).
In modes 4, 5, 6, and 7, the DAC:
• operates as a DTE
• monitors the DSR
• monitors DCD control leads
• drives the DTR lead
The RI lead is ignored. No menus or prompts are given when DCD is OFF.
All prompts and messages are enabled for inbound calls and disabled for
outbound calls. See Figure 88 on page 438 for more details.
In modes 4 and 5, the DAC drives the DTR lead OFF in the idle state, and ON
when processing an incoming or outgoing call.
In modes 6 and 7, the DAC drives the DTR lead ON except when the call is
being disconnected. At disconnect, DTR is dropped for 0.2 seconds and then
returns to ON.
With outbound gateway access, the DAC answers the data call and drives the
DTR lead ON (modes 4 and 5; in modes 6 and 7, DTR is already ON). Then
the calling data module and the DAC form a transparent link between the
calling Data Module (DM) and the gateway. The DM user may then enter the
appropriate commands to the gateway to establish a data call. The DAC
expects the gateway to drive DCD ON (modes 4 and 5 only) within
35 seconds. If the gateway fails to do so, the DAC turns DTR OFF and drops
the call. When the call is established, the gateway may cause the DAC to
disconnect the call by dropping either DSR or DCD.
For inbound gateway access, the gateway must drive the DCD lead ON to
activate the DAC. When the DAC receives this signal, it drives the DTR lead
ON, makes the unit busy for outbound calls (modes 4 and 5; in modes 6 and
7, DTR is already ON), and prepares to accept <CR> for autobaud. The DAC
expects DCD to remain ON for as long as the data call is established.