In the Pass-through mode, the firmware on the device detects the tones of the call for fax, modem, or TTY. The firmware then uses G.711 encoding to carry the call over the IP network. The Pass-through mode provides high-quality transmission when endpoints in the network are all synchronized to the same clock source.
Note:
The Pass-through mode increases the bandwidth use of each channel. However, you can make the same number of simultaneous fax or modem calls on the device as voice calls.
Note:
For the Pass-through mode on a modem and TTY calls over an IP network, the sending and receiving servers must have a common synchronization source. Using a source on the public network, you can establish synchronized clocks.
