Allied Telesis AT-VP504E FXS (H.323) - Manual (Page 12)

Chapter 1 - Making Calls with the AT-VP504E FXS User’s Manual (H.323 Version)
AT-VP504E FXS 8
Calls Involving a PSTN Gateway
The following example illustrates how a telephone/fax connected to an
AT-VP504E FXS terminal and a PSTN phone can communicate via a
PSTN gateway.
Phone/Fax -> AT-VP504E FXS -> AT-VP504E FXO (Gateway) ->
PSTN
A user makes a call with the phone/fax connected to an AT-VP504E FXS,
which in turn contacts an AT-VP504E FXO gateway, then reaches the
corresponding PSTN Phone.
A PSTN user can also contact the AT-VP504E FXO gateway, which in
turn contacts the AT-VP504E FXS, then reaches the corresponding phone/
fax.
IP / LAN
Telephone
AT-VP504E FXS
Fax
Gatekeeper
PSTN Phone
PSTN
4 telephone lines
connected to the PSTN
AT-VP504E FXO
(Gateway)