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CHAPTER 4: DEFINITIONS OF 7500 OPTIONS
Mode
Configurations: Asynchronous DCE, Asynchronous DTE, Synchronous DCE
Asynchronous DCE
Mode selects the preferred data protocol your 7500 will use to originate a data call. This option only
refers to data call origination. Incoming calls, in contrast, are always answered with the data protocol
specified by the caller. To find out which values of the Mode option you can select, contact your
system administrator. Data calls will not work unless your telephone line has been administered for the
data service you will be using (that is, X.25 for D-Channel packet switched data service and Mode 2 or
Mode 3 for B-Channel circuit switched data service). The values of this option are described as follows:
BA:
B-channel adaptive from Modes 3 and 2 (BA). For outgoing calls, if you select
this value, the 7500 will attempt to establish a circuit switched Mode 3 call. If
the system you are calling can not accept this type of call, the 7500 will attempt
to establish a circuit switched Mode 2 data call. Mode 3 can cause slightly
higher delays on transmitted and received data than Mode 2, but it provides
automatic error correction. Mode 3 also uses the Packet Assembler Disassembler
(PAD) options in the same manner as X.25.
DX25:
X.25 (DX25) packet data on the D-channel.
B2:
Mode 2 circuit switched data on the B-channel. If you select this value for
outgoing calls, the 7500 will attempt to establish a Mode 2 call. Mode 2
provides the least amount of delay on transmitted and received data, but it does
not provide error correction. As such, this mode emulates conventional analog
data transmission.
Mode 2 and Mode 3 are defined in the AT&T Digital Multiplexed Interface (DMI) Technical
Specification. (For a copy of this manual, Document number 500-029, call the Customer
Information Center, at 1-800-432-6600.)
The Mode option only refers to data call origination. Also: a Mode 2 data call cannot be
established between two Mode 2 DTE endpoints.
If the user escapes to Local Mode while the far end is transmitting Mode 2 data, this data may
be lost.
If this option is changed during an active data call, it will not take effect until the next data
call.
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