Difference between FXS and FXO

FXS and FXO are the interfaces for analog phone lines, and it is also called POTS (Plain Old Telephone Service). FXO and FXS are always paired. FXS and FXO are terms used in telecommunications to show whether VoIP equipment is equipped to support analog lines (FXO) and analog phones (FXS).

What is FXS?

FXS is the abbreviation of Foreign Exchange Subscriber. It is a port that connects the access server or router to end users’ equipment such as modems, office phones, or fax machines. FXS is the plug on the wall and provides telephony services and supplies battery power, provides generates ringing voltage and dial tone, in order to transmit the analog signal.

what is FXS

What is FXO?

FXO is the abbreviation of Foreign Exchange Office. It is the plug on the end communication device, such as a fax machine or office phone. At the FXS end of the telephone circuit, FXO receives telephony services and creates on-hook and off-hook indicators. The FXO links the device to the FXS port, and also to the external phone line, requesting the dial tone required to make a call.

How does It Work?

If you connect an FXS device to another FXS device, it will not work. Similarly, if you connect an FXO device to another FXO device, it will not work either. A telecommunications line from an FXO port must connect to an FXS port in order for the connection to work. Similarly, a line from an FXS port must connect to an FXO port. When the FXO port on your analog telephone is connected to the FXS port in the wall, then you can make phone calls.

About VoIP Gateway

A VoIP gateway is a hardware device that can convert analog telephone signals into digital signals, and can convert calls between an Internet-based IP network and traditional copper wire fixed telephones for the transmission of voice data. After converting the signal, the VoIP gateway organizes it into data packets and encrypts them for transmission. VoIP providers use VoIP gateways for switching and network interfaces.

stm1 over gigabit VOIP gateway

STM-1 over Gigabit Ethernet 63E1 VOIP Trunk Gateway

As we have talked about earlier, more information about VoIP Gateway is in this article, click here to read ‘What is a VoIP Gateway?

FXS voip gateway


FXS is a plug on the wall and FXO is a plug on the phone. FXS provides dial tone, whereas the FXO requests dial tone. If you have a company using a telephone system, FXO ports are necessary on the phones because they are allowed to dial traditional, analog telephones. If you have any questions, you can contact Baudcom.

Baudcom offers all kinds of FXO FXS devices. For more information, please visit www.baudcom.com.cn.

Post time:2023-07-09


Lomoveishiy – Finland

I needed those to connect my PC on the third floor to have internet access in that room, and ISP installed their modem on the first floor only. After dropping fiber patch cables, plugged in all cables into these media converters at both sides, and link came up instantly. Was much easier than I thought!

Raymond – USA

Great experience – units worked straight out of the box – just needed plug in cables and we were done. I also like the possibility to enable jumbo frames, while we do not have a need for this feature at the current moment it’s great to have this option.

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