[Asterisk-Users] building a phone recorder

[Leo Ann Boon]

David Powers wrote:

> How feasible would it be to build a phone recorder with Asterisk 
> (takes a number of analog phone lines in and records them when there 
> is conversation).  Has such a thing already been done or are there 
> aspects of such a thing that would require significant changes to 
> Asterisk to handle?
>

I assume you're referring to using * as a voice logger to record 
existing phone lines? The short answer is no. * can only record calls 
that are passing through itself. The long answer:
a) A typical voice logger is attached in parallel to the target phone. 
The FXO port on the logger can only listen passively without generating 
any signal. If you just plug * (X101P or TDM FXO) in parallel with the 
phone, * will pull the line down the moment it kicks in to record. Most 
like your current call will experience distortion - just like what 
happens when one person tries to pick up a phone while another is on a 
parallel phone.

b) To minimize interference, the recording port must have a high 
impedence bridge or 'High-Z bridge'. There're voice cards on the market 
that have High-Z bridge built-in. These are purpose built for voice 
logging. At this point of time, there're no * driver for any of these. 
And, I'm not sure if * will need custom changes to support voice 
activated recording, etc.

Some companies that produce High-Z logging cards:
- Voicetronix (http://www.voicetronix.com/vpb8i.htm) - very nice with 
Linux drivers and open-source logging s/w
- Cybertech (http://www.cybertech.nl) - Witness logger uses these cards
- Ai-Logix (http://www.ai-logix.com/products.html) - Used by Eyretel 
(now part of Witness)
-  Intel/Dialogic 
(http://www.intel.com/design/network/products/telecom/boards/signaling.htm#ltb)
FYI.