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Chapter 3 - Software Installation and Configuration
MTA128ST-USB
Call Control Configuration
Persistent DTR Dialing _______________________
A high DTR (Data Terminal Ready) signal on the USB port indicates your computer or
terminal is ready to communicate with your MTA128ST-USB. DTR normally goes high
when a communication program starts or is ready to dial. Persistent DTR dialing enables
the unit to automatically redial the number stored in memory location 0 whenever DTR is
high and the USB port does not have an active call. You can enable or disable this
feature. AT command: $D.
Auto Answer Data Calls _______ Rings to Answer ___________
Select Auto Answer if you want your MTA128ST-USB to automatically answer all
incoming data calls (this option does not affect the analog port). The Rings to Answer
number, in the range of 1 to 255, selects the number of rings the unit waits before
answering an incoming call. The default is one ring. AT command: S0=
Dialing Method _____________________________
Select either the Enbloc or the Overlap dialing method for use when establishing a data
call. Your ISDN provider determines the dialing method. The Enbloc method is used for
most ISDN dialing; however, you can select the overlap method if you are working with a
private network. AT command: %A97=
Data Protocol ________________________________
The data protocol, also known as the B-channel protocol and the rate adaption protocol,
is the language spoken over each 64 Kbps channel between two ISDN devices. The
devices on both ends of the ISDN link must use identical protocols. AT command: !Z=
• V.110 Protocol—Used to connect slower, pre-ISDN communications devices to
high-speed ISDN lines. It handles rates up to only 38400 bps and is used mostly in
Europe. The devices on both ends of the link must be set to identical rates. However,
the MTA128ST-USB (by default) is able to adapt to the network rate of a received
V.110 call even though it has S76 or $MB set to a different network rate.
• V.120 Protocol—Similar to V.110 protocol, but provides rates up to 64000 bps on
each B channel.
• X.75 Protocol—Packet-switched network protocol for international use. Layer 2
portion of this protocol is used commonly as a rate adaption protocol.
• MLPPP Protocol—MLPPP (Multi-Link PPP) protocol provides rates up to 64 Kbps
per channel. This protocol uses both B channels at once, providing an aggregate
data transmission speed of 128 Kbps.
Dialing Numbers _____________________________
The MTA128ST-USB can dial telephone number n, where n can be up to 20 characters.
AT command: Dn (n = phone number).
Stored Numbers _____________________________
The MTA128ST-USB can store as many as ten phone numbers, up to 20 characters
each. AT command: &Z=
Dialing Stored Numbers _______________________
The MTA128ST-USB can dial a number previously stored in directory number n with the
&Zn=x command. AT command: e.g., DSn