Difference Between FXO and FXS

FXO vs FXS

Foreign Exchange Subscriber(FXS) and Foreign Exchange Office (FXO) are two of the most common interfaces used in analogue telephony.

FXO can be described as a plug on the phone, and FXS as a plug on the wall.

While an FXO devise connects to an office, the FXS connects to a station. Another difference that can be noticed between the two, is that the FXS provides dial tone, whereas the FXO requests dial tone.

The FXS provides dial battery, loop current and ringing voltage. On the other hand, the FXO receives ringing voltage. Another difference that can be seen, is that while the FXS receives touch tone digits, the FXO requests dial tone. When the FXS sends CLID, the FXO captures and interprets CLID.

Foreign Exchange Office receives the Plain Old Telephone Service (POTS) from the Public Switched Telephone Network (PSTN). Well, FXO can be said to be directed towards the Telecom office. On-hook and off-hook indication, or loop closure, changed the primary services provided by an FXO interface to the Telco network device.

Foreign Exchange Subscriber delivers Plain Old Telephone Service from the telephone company’s central office, and has to be connected to a telephone, Fax machine or modem. The FXS is directed at the telephone subscriber. Dial Tone, Ring Voltage and Battery Current are some of the primary services an FXS interface provides.

An FXS is a device that receives a call, and an FXO is a device that initiates a call.

How does an FXS receive a call? It receives calls by detecting the line that has been seized, which means that the FXO goes off the hook. It also receives Dual-Tone Multi-Frequency digits, which indicate how calls should be routed.

The FXS devise supplies about 50 volts DC power to the line. In an emergency, FXO devices use the FXS line voltage for power, to remain operable in case of a power failure. The FXO initiates a call by going off-hook, which helps in seizing telephone line. The devise identifies the destination through the Dual-Tone Multi-Frequency digits.

Summary

1. FXO is a plug on the phone, and FXS, a plug on the wall.

2. FXS provides dial tone, whereas the FXO requests dial tone.

3. While the FXS receives touch tone digits, the FXO requests dial tone. Where the FXS sends CLID, the FXO captures and interprets CLID.

4. An FXS is a device that receives a call, and an FXO is a device that initiates a call.

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