Why are there FXO cards, and FXS cards? What's the difference, and why is it needed? Modem cards, seem to be able to dial out, and receive calls, so why are these cards different?
Shaoul Jacobson - TELLINK
2005-May-02 03:29 UTC
[Asterisk-Users] Diffrence bewteen FXO and FXS
Hi, First, do forgive any syntax or language errors as English is not my mother tongue. To make a 'long' story short, - let's look at a phone home. The public switch (the very big machine at your telco) provides power to the line. This power gives energy to your phone. This is how a 'standard' phone can work without external power adaptor. So, the public switch sends power, the private phone receives power - lets look at a small office there is a pbx (private box) it is connected to the public phone line(s) it receives power on those lines from the public switch (also it will use the 110-240V power lines for real power) it is connected to several insides phones. It provides power to those inside phones like the public switch does. So, some interfaces receive power, others send power. You can also think as male and female plug. You plug the male with a female Likewise, you connect a fxo to fxs. 'Fxo to fxo' or 'fxs to fxs' will not work and in one case even bring problem as the two are sending power. The public switch is most of the time rather protected against most things, but your card not always. So you can send some circuit to silicon heaven. Some googling will provide similar (or better) explanations Shaoul Jacobson Senior VoIP Consultant Tellink Tel : +32 3 201 96 36 Fax : +32 3 227 09 81 e-mail shaoul@tellink.com -----Original Message----- From: Mr AG!! [mailto:angelisonline@gmail.com] Sent: lundi 2 mai 2005 11:12 To: asterisk-users@lists.digium.com Subject: [Asterisk-Users] Diffrence bewteen FXO and FXS Why are there FXO cards, and FXS cards? What's the difference, and why is it needed? Modem cards, seem to be able to dial out, and receive calls, so why are these cards different? _______________________________________________ Asterisk-Users mailing list Asterisk-Users@lists.digium.com http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
Mr AG!! wrote:>Why are there FXO cards, and FXS cards? What's the difference, and why >is it needed? Modem cards, seem to be able to dial out, and receive >calls, so why are these cards different? > >FXO card = plug to phone line FXS card = plug to regular phone FXS provides power to phone. FXO takes power from phone line. Don't plug PSTN in your FXS card or you could fry it... Cheers, Jean-Michel. -- Ykoz Un Max - La VoIP en pr?-pay?! Essayez gratuitement - 5 cr?dits offerts. ---> http://ykoz.net/voip/max <---
Shaoul Jacobson - TELLINK
2005-May-02 04:27 UTC
[Asterisk-Users] Diffrence bewteen FXO and FXS
Hi, FXS card = plug to regular phone FXO card = plug to phone line The trick I use is: FXO with a 'O' as in Office. This is where you plug your phone A FXO card emulates a phone (receives power) FXS with 'S' as in (public) Switch This is the part that gives power A FXS card emulates a switch (gives power) Plugging 2 FXS elements together is not a good idea Plugging 2 FXO elements together will not work but no problem otherwise Shaoul Jacobson Senior VoIP Consultant Tellink Tel : +32 3 201 96 36 Fax : +32 3 227 09 81 e-mail shaoul@tellink.com
Eric Wieling aka ManxPower
2005-May-02 05:00 UTC
[Asterisk-Users] Diffrence bewteen FXO and FXS
Mr AG!! wrote:> Why are there FXO cards, and FXS cards? What's the difference, and why > is it needed? Modem cards, seem to be able to dial out, and receive > calls, so why are these cards different?For one thing, modem cards do not generate a ring voltage (they just pass it thru from the telco. Same for the dialtone.
Here is an excellent document explaining the differences between FXO and FXS. http://www.google.com/url?sa=U&start=5&q=http://www.patton.com/technotes/fxs_fxo.pdf&e=7385 Also you can look at Digium's site for their description, which describes it from a stand point of Asterisk as the PBX. http://www.digium.com/index.php?menu=fxsvfxo> Why are there FXO cards, and FXS cards? What's the difference, and why > is it needed? Modem cards, seem to be able to dial out, and receive > calls, so why are these cards different?