Flow Control; Autobaud; 4-Wire Operation; 2-Wire Leased-Line Operation - Black Box 325 User Manual

MODEM 325 AND MODEM 325 CARD

5.6 Flow Control

Flow control adjusts for differences in speed between the modem and DTE. The DTE can operate at a
constant speed independent of the bit rate of the modem.
Flow control works in both directions. The modem can start and stop the DTE transmitter and the
DTE can start and stop the modem transmitter. Both inband and out-of-band flow control are
implemented. Inband methods employ the characters DC1/DC3 (11 hex / 13 hex). Out-of-band flow
control is accomplished with the CTS and RTS interface leads.

5.7 Autobaud

With autobaud, the modem will automatically detect DTE speed and adjust to communicate with the
DTE at that rate as soon as it receives the first "AT." The protocol processor will default to 9600 bps.
Autobaud also detects the character size and parity used by the DTE.
Autobaud overrides the LCD selection for DTE speed, character length, and parity.

5.8 4-Wire Operation

When configured for 4-wire operation, the modem is a full-duplex leased-line modem requiring a
dedicated 4-wire leased line. Only point-to-point dedicated leased lines are supported. The 4-wire leased
line is connected to the TELSET/LEASED LINE jack on the rear panel. Dialing is not necessary. When
connected via leased line, the modems will train and begin communicating with each other. The DIAL
jack can be used to connect a 2-wire PSTN line for dial backup.
One modem must be configured for forced answer and MNP options must be the same on
both ends of a 4-wire leased line for the connection to be successful.
4-wire leased-line mode supports 4800 and 9600 rates only and incorporates a CCITT V.33-
like training sequence. The modem will not connect with a 4-wire leased-line modem using
a CCITT V.32-type training sequence.
5.9 2-Wire Operation
When configured for 2-wire operation, the modem is a full-duplex modem able to operate over 2-wire
leased or PSTN lines.
5.9.1 2-W L -L
IRE EASED
The 2-wire leased line is connected to the TELSET/LEASED LINE jack; the DIAL jack is used to connect
a 2-wire PSTN line for dial backup. The leased line connects the local and remote modems directly, so
dialing is not necessary. One of the modems must be configured for FORCED ANSWER. When
connected via leased line, the modems will train and begin communicating with each other.
4 4
O
INE PERATION
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