TC Communications TC1901 User Manual page 16

FXO-Foreign Exchange Office.
FXO configuration is required for a plain old telephone service (POTS) to generate a call to the telephone
network.
FXS-Foreign Exchange Station.
FXS configuration is required for a telephone network to generate a call to a plain old telephone set.
Hotlink-direct connected phone line.
PBX-Private Branch Exchange.
A telephone exchange device owned by private entity.
Ringdown-provide ringing signal.
Toll quality voice-voice frequency is restricted within 300Hz to 3.4KHz.
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TC1901
User's Manual
Rev. 1.8
MNL-19010-01-18