[cisco-voip] FXS/FXO - Fax Lines?

[VM]

POTS = Plain Old Telephone Service
FXO = Foreign Exchange Office (i.e. TELCO Switch)
FXS = Foreign Exchange Station (i.e. analog telephone)

For some reason, Cisco identifies these hardware components by the  
devices that are intended to be connected to it such that FXS devices  
(analog phones, modems, faxes, etc.) connect to the FXS cards and the  
FXO cards connect to analog lines being provided with line current  
and voltage.  However, the FXO card is actually a FXS device (acts  
line a station expecting line current and voltage) and the FXS card  
is actually a FXO device (acts like a Telco switch providing line  
current and voltage).

Connecting FXS devices to Cisco FXO cards will not work.

On Oct 29, 2007, at 11:43 AM, Matthew Saskin wrote:

> At the simplest:
> FXS provides battery current and ring voltage
> FXO receives battery current and ring voltage.
>
> They are not interchangeable - FXO's will be used when terminating an
> analog log provided by a PABX, from a telco, etc.
>
> FXS ports are necessary when you need to generate dial-tone/ring,  
> i.e.;
> for analog phones, fax machines, etc.
>
> -matt
>
> Weigand, John V. wrote:
>> 	
>>
>> Litigation Management
>>
>> 	
>>
>> Serious Medicine for the Defense ® <http:// 
>> www.medicineforthedefense.com/>
>>
>> 	
>> 	
>>
>> This may seem like a stupid question, but I’m having trouble grasping
>> the difference between FXS and FXO ports. Currently, we have all our
>> POTS fax lines going out through FXS ports on our Callmanager  
>> gateways,
>> which is the way our VAR set it up. Can we setup those FXO ports  
>> as POTS
>> lines and attach fax machines to those, or will that not work?
>>
>>
>>
>> Thanks in advance.
>>
>>
>> 	*John V. Weigand*
>> Help Desk Support
>>
>> Litigation Management, Inc.
>> 300 Allen-Bradley Drive
>> Suite 200
>> Mayfield Heights, OH 44124
>>
>> 	
>>
>>
>>
>>
>> Tel:
>> Fax: 440-484-2020
>> Cell:
>> email: <mailto:jvw at medicineforthedefense.com>
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