Resolviendo problemas de colgado en tarjetas FXO

Cuando instalamos tarjetas  ya sea Digium TDM410P,  TDM400P, Openvox A400P con modulos FXO muchas veces sucede que Asterisk no detecta  la  senal de colgado, Por ejemplo  un cliente llama  a nuestro IVR pero  antes de selecionar una opcion cuelga  la llamada. Pero si miramos en  el FOP veremos aun la linea abierta. Otro caso es que llaman  a una extension  y les  recibe el correo de voz y cuelgan la llamada, Pero aun asi encontramos correos de voz mudos con horas de grabaciones.

Bueno aqui les dejo algunas posibles  soluciones muy efectiva paras solucionar este problema.  ,

En  el archivo chan_dahdi.conf

Descomentamos la opciones :

;busydetect=yes
;
; On trunk interfaces (FXS) it can be useful to attempt to follow the progress
; of a call through RINGING, BUSY, and ANSWERING. If turned on, call
; progress attempts to determine answer, busy, and ringing on phone lines.
; This feature is HIGHLY EXPERIMENTAL and can easily detect false answers,
; so don't count on it being very accurate. Also, it is ONLY configured for
; standard U.S. tones
;
;busycount=4
;
;callprogress=no

Lets explain what those 3 options mean:

busydetect: 

With this option enabled, asterisk will try to 'listen' for busy signals on the line, if your carrier sends you a busy tone on a hangup, this should detect it. (Note that this is not exact science, asterisk might think your cat screaming is a busy tone and hangup. In case of loopstart in zapata.conf, you will certainly need this.

To avoid this, they invented the next option, 

Busycount:

Busycount defines the amount of busy tones asterisk needs to recognize before actually considering the line to really really give a busy tone, to avoid false hangups on non hangup sounds.
The standard setting is 3, but you could change that to 6 or 10 if you would want to.

A side effect is, that it will take longer to detect a hangup and in case of a real hangup, the line will stay occupied for a little longer than with a lower value of busycount.

callprogress: 

This option is similar to the busydetect option, but will also listen for a ringing tone, congestion tone and will try to detect if the line got answered.
It might work for you, but its highly unreliable and will probably give many false hangups.

Please note that none of these 3 options should be activated on digital zaptel channels, (BRI, PRI) as they will not help with anything, they will just cause false hangups).

When you get the reverse polarity to work, dont use these options either.

3) Check your signalling settings in zapata.conf:

; fxs_ls: FXS (Loop Start)
; fxs_gs: FXS (Ground Start)
; fxs_ks: FXS (Kewl Start)
signalling=fxs_ks

The correct choice for the signalling= line depends on your carrier.
When you call them with this question they probably wont have a clue what you are talking about so trying several might be a good idea.

Kewl start is the best option there is, but it might not work in your situation, try to call your telco and ask for "disconnect supervision"
In this case, the telco will cut the power on the 2 telephone lines for a small period of time or will reverse the polarity on the lines.

(You could check this by calling to that pstn line, and connecting a phone with a lighted keypad and without external power supply there).
If the lights go out when the other end disconnects, the telco has disconnect supervision.

Loop start does not send a hangup signal, you will need the busydetect parameter.

http://www.asteriskguru.com/tutorials/resolving_hangup_detection_problems_fxo_tdm_voicemail.html