Modemulator User Guide
Page
29
of
113
The
remote
Modemulator will report
NOT FOUND
if an entry for that phone number is not found in
the dialing directory, and a dial-up modem is not attached or not available. See
Compatibility With Dial-up Modems
for information about attaching a dial-up modem to a
Modemulator.
If an entry for that phone number is not found in the dialing directory, and a dial-up modem is
attached and available, the
remote
Modemulator will forward the dial command to the attached
dial-up modem which will dial the number via the PSTN. See
Maintain Compatibility With Dial-up
for information about attaching a dial-up modem to a Modemulator.
The legacy software sends the same type of command to initiate the cellular connection as it does for an
analog connection, and receives the same type of responses. This makes the cellular connection
indistinguishable from an analog connection to the legacy software.
Modemulator Incoming Calls
In a single-ended system that uses conventional cellular service, the
host
will be unable to initiate a
connection to the
remote
Modemulators because of constraints in the cellular network, unless a VPN
tunnel or public static IP address is used.
The cellular service provider normally assigns dynamic IP addresses to the cellular devices, which
prevents the
host
from knowing the current IP address
of the
remote
Modemulators.
The cellular service provider may have a firewall preventing any
host
from contacting the IP
address
of any
cellular devices.
The following diagram illustrates a simplified single-ended legacy system using one Modemulator and
conventional client/server cellular service.
