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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
Follow the set-up for
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.
Modemulator User Guide
peer-to-peer operation
to program the host Modemulators dialing directory with IP
Page 30 of 113
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