Nortel Circuit Card Installation Manual page 463

Table 158
Connect and disconnect protocol (Part 3 of 12)
Mode of
operation Interface application
Mode 1 Inbound Hotline modem
pools
Most dumb modems can be
used for this application.
Mode 2 Inbound and Outbound
modem pools (with forced
DTR)
Use this mode with Hayes
1200 modem.
NT7D16 Data Access card
Comments
Inbound Hotline modem pooling:
Modem sends ring/no ring cycle (2 seconds ON, 4
seconds OFF) to initiate connection.
DAC responds by trying to establish a Hotline call
to a specific Data Module (Autodial).
When Data Module answers, then and only then,
the DAC turns DTR ON.
Modem should answer the incoming call when
DTR goes ON and should turn DCD ON within 35
seconds; otherwise the DAC disconnects the call.
Call disconnection:
Disconnection is the same as mode 0.
Inbound and Outbound modem pooling:
The DAC operation is identical to mode 0 except
that DTR is always forced ON (except during
disconnect).
Call disconnection:
Disconnection is identical to mode 0 except:
—When a call is released, the DAC turns DTR
OFF for 0.2 second and then ON. DTR stays ON
until the next call release.
—The DAC ignores RI and DCD for about 2
seconds after releasing a call. This avoids
problems with the Hayes 1200 modem.
Circuit Card
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Description and Installation