Modems - Computer Busses - page 250

an outside line is required (in Australia it is a '0', by contrast). A delay is normally required
after the 9 prefix before dialing the actual number. To modify the delay to 5 seconds, dial the
number 9 0112432 and wait 30 seconds for the carrier, then the following command line can
be used:

ATDT 9,0112432 S8=5 S7=30

It can be seen in Figure 15.4 that a prefix and a suffix are sent to the modem. This is to en-
sure there is a time delay between the transmission prefix and the suffix string. For example,
when the modem is to hang-up the connection, the ' +++ ' is sent followed by a delay then the
' ATH '.
In Figure 15.4 there is an option called O riginate. This string is sent initially to the mo-
dem to set it up. In this case the string is ' ATQ0V1E1S0=0 '. The Q0 part informs the modem to
return a send status code. The V1 part informs the modem that the return code message is to
be displayed rather than just the value of the return code; for example, it displays CONNECT
1200 rather than the code 5 (V0 displays the status code). The E1 part enables the command
message echo (E0 disables it).
Figure 15.6 shows the modem set-up windows for CompuServe access. The string in this
case is:

ATS0=0 Q0 V1 &C1&D2^M

as previously seen, S0 stops the modem from auto-answering. V1 causes the modem to re-
spond with word responses. &C1 and &D2 set up the hardware signals for the modem. Finally
^M represents Cntrl-M which defines the carriage return character.
The modem reset command in this case is AT &F . This resets the modem and restores the
factor default settings.

Figure 15.4 Modem commands

Figure 15.5 Dialling a remote modem