Modemulator User Guide
Page
30
of
113
Maintain Compatibility with Dial-up Modems
The
host
Modemulator of a peer-to-peer system can utilize an attached serial dial-up modem for
connections with
remote
dial-up modems via the PSTN. This section describes a system that has a
mixture of
remote
Modemulators and
remote
dial-up modems.
A mixed cellular / dial-up system requires:
Cellular peer-to-peer service for the
host
Modemulator and
remote
Modemulators
PSTN service at the
host
site and at all
remote
dial-up
sites
A serial dial-up modem attached to the
host
Modemulator at the
host
site
A dial-up modem attached to the
remote
application hardware at each
remote
dial-up
site
host
Modemulators dialing directory with IP
addresses for the
remote
Modemulators.
Do not enter the PSTN phone number of any
remote
dial-up
site into the
host
Modemulators
dialing directory.
The
host
Modemulator can initiate or answer PSTN connections by using an attached serial dial-up
modem. Also, any configuration commands sent to the Modemulator are processed by both the
Modemulator and by the attached modem. In that way, modem initialization strings sent by legacy
software will apply to both the Modemulator and the dial-up modem.
Outgoing PSTN Calls
For a PSTN connection to be initiated, a dial command is sent to the
host
Modemulator by the legacy
software. The
host
Modemulator will search its dialing directory for an entry containing the phone
number in the dial command.
If no entry is found for that phone number, the dial command will be forwarded to the attached
dial-up modem which will dial that phone number via the PSTN, allowing the legacy software to
contact any
remote
dial-up site.
The
host
Modemulator will report
NOT FOUND
if a PSTN phone number is dialed and a dial-up
modem is not attached or not available based on the RS232 CTS signal.
The legacy software sends the same type of dial command to initiate either cellular or PSTN connections,
and receives the same type of responses. This makes the type of connection indistinguishable and
transparent to the legacy software.