[Asterisk-Users] TDM400P FXS polarity reversal?

[Soren Rathje]

Rich Adamson wrote:
>> Is it possible to do a talk battery polarity reversal on a TDM400P
>> FXS interface?  Everything I can find seems to be referring to the
>> procedure for detecting a battery reversal on a telephone company
>> POTS line using the FXO interface, but not for actually generating
>> one back to a station upon answer supervision.  I would assume that
>> VoicePulse and VoipJet provide a way of signaling far-end
>> supervision back to the originating Asterisk PBX...
>>
>> Basically, my two questions are:
>> (1) Is the hardware capable of even performing a reversal?
>> (2) If the above is true, how would you make it happen in Asterisk?
>
> The Silicon Labs spec sheet does not specifically indicate generating
> a reversal is possible. Therefore, best guess is the integrated
> circuits on the card does not support it, therefore asterisk has no
> means of doing it.
>

Specs for Si3210 (TDM400P FXS Module) says on page 93:

---
Register 72. On-Hook Line Voltage

Bit 6 VSGN On-Hook Line Voltage.
The value written to this bit sets the on-hook line voltage polarity
(VTIP–VRING).
  0 = VTIP–VRING is positive
  1 = VTIP–VRING is negative
---

I wonder if this can control Pol-Rev's.. ?

/Soren