[asterisk-users] Zaptel FXS Cards - Station Distance

[John Novack]

Kevin P. Fleming wrote:
> Tim Nelson wrote:
>   
>> Hello! In the near future, I'll be deploying an asterisk system that will have (in addition to many SIP handsets) four FXS handsets. Is there a known limitation to the length of cabling that can be used between a Digium/Openvox/Sangoma FXS card and the end station? I understand the card will need a molex power connector plugged in to provide extra voltage. With traditional phone systems, I have not seen any distance limitations. I would just like to verify that the FXS ports are able to provide sufficient power for longer runs. Thank you!!!
>>     
>
> You don't quote any numbers here, and 'longer' is not anything we can
> relate to.
>
> However, I can say that the FXS line drivers on Digium analog modules
> should be able to handle 1000' runs or so, but not more than that. This
> should be equivalent to what any standard PBX with FXS ports can do,
> unless it has special 'long line' drivers.
>   
In reality many PBX analog circuits using DTMF only can go quite a bit 
longer. The  1K foot limitation with pulse dial is more realistic, due 
to cable capacitance mis shaping of pulses. DTMF only is limited by the 
line resistance limiting current to 20-30 Ma required to operate the 
tone pad. More modern ( cheap Chinese ) phones often will operate with less.
With lower than normal 48VDC supplies, the distance grows ever shorter.
So, what is the distance you require?
What is the size of the wire in the cable?

Dial long line circuits ARE available, and advised along with special 
protection if the stations will be off premises.

John Novack

-- 
Dog is my co-pilot