VoIP Gateway: What Is the Difference between FXS and FXO?

In Voice over Internet Protocol (VoIP) telephony, a VoIP Gateway is a device that enables the conversion of traditional analog telephony signals to digital IP-based signals, allowing communication between traditional telephone networks and IP networks. Within a VoIP Gateway, you'll often encounter terms like FXS and FXO, which refer to specific interfaces used to connect analog devices to the VoIP system. These interfaces serve different purposes in connecting to the Public Switched Telephone Network (PSTN) or analog devices. Here's the difference between FXS and FXO:

FXS (Foreign Exchange Station):

An FXS interface is used to connect analog devices such as telephones, fax machines, or analog modems to a VoIP network. FXS interfaces provide power and signaling to these analog devices, enabling them to function as they would on a traditional phone line. Key features of FXS include:

• Provides Dial Tone: FXS interfaces provide a dial tone to the connected analog device, similar to what users experience on a standard telephone line.

• Supplies Power: FXS interfaces supply electrical power to the connected device, allowing it to function without needing an external power source.

• Ring Voltage: FXS interfaces provide the ring voltage to alert the connected device of incoming calls.

• Initiates Calls: Analog devices connected via FXS interfaces can initiate outgoing calls by accessing the dial tone and dialing a number.

FXS Series Voip Gateway

FXO (Foreign Exchange Office):

An FXO interface is used to connect a VoIP Gateway or IP-based phone system to the traditional telephone network (PSTN). FXO interfaces connect to analog lines provided by the telephone company or to analog ports on Private Branch Exchange (PBX) systems. Key features of FXO include:

• Receives Dial Tone: FXO interfaces receive the dial tone from the PSTN or PBX system, allowing the VoIP system to initiate calls.

• Detects Ringing: FXO interfaces detect the ringing signal from the PSTN or PBX system, indicating incoming calls.

• Provides Disconnect Detection: FXO interfaces detect when a call is disconnected, allowing the VoIP system to release the line.

• Cannot Initiate Calls: FXO interfaces cannot initiate outgoing calls themselves; they rely on the VoIP system to initiate calls.

  
  

  FXO Voip Gateway
  

In summary, FXS and FXO interfaces serve complementary roles in a VoIP Gateway or IP-based phone system. FXS interfaces connect analog devices to the VoIP network, allowing them to interact with IP-based communication. FXO interfaces connect the VoIP system to the traditional telephone network, enabling the system to communicate with analog lines provided by the PSTN or PBX systems.