8 IP Modem Function
8.5.1 AT D (dial)
This is the general Dial command. The target is defined as IP Address plus TCP-port number. The
dots in the address are replaced by a comma, and the TCP port is also separated by a comma. On
normal modems a comma generates a pause in the dialing sequence. This is commonly required,
so all software will support it; even multiple comma.
The modifiers ‘T’ for Touch Tone and ‘P’ for Pulse dialing have no direct equivalent on the TCP
connection. They are used to change between Modem and Host mode, if the ATB command enables
this (ATB2 or ATB3). Otherwise the IP Modem will ignore them.
Basically dialing is done to a given IP Address plus a TCP port number. The IP Address is given in
decimal Octet format, where comma replaces the dot as the separator. This is followed by another
comma, separating the TCP Port from the IP Address. If the port is omitted, the target port is
the same as the local TCP Data Port as defined in the configuration of IP Modem (see
6.2.2.2.7
above).
There are situations where the target is known by a DNS name. This name can not be used in a
dial string, mostly because very few software will support it. So there is the option of dialing to a
pre-defined entry by shortcut. This is given by an ‘S’ followed by one or two digits. The shortcuts
S90 to S99 are reserved; so far only S1 to S4 are implemented. Shortcuts are defined and saved by
‘AT&Znn=<FDN:Port>’.
All other non-numeric characters are understood as modifiers. The IP Modem will simply ignore
them. This especially applies to space characters. Typically dial strings are:
ATDT192,168,254,254,2003<cr>
Dial another IP Modem as a Modem-to-Modem
AT&Z12=demokit.vscom.com.tw:23<cr>
Define a shortcut for configuration port
ATDPS12<cr>
Dial the other IP Modem as Modem-to-Host
Table 23: IP Modem Sample Dials
8.5.2 AT O (online / data mode)
If a connection is established, the IP Modem can still be in command mode. The ATO activates
the transparent data mode.
8.5.3 AT A (answer call)
Have the IP Modem answer an incoming call, and establish a TCP connection. This command is
required if Auto-Answer is disabled. Observe the operation mode defined by ATB.
8.5.4 AT B (modulation) [ATB1]
This command is used to define the modulation to use on the phone line. Since the only "modula-
tion" available is IP, there is no choice. The command is used to change between Modem-to-Modem
and Modem-to-Host mode.
September 2016
NetCom Plus User Manual
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