January 04, 2004

ATAs and Home Wiring

About a month back a poster in LightReading posted that “VoIP will be a nice (sic, should be niche) product deployed as a last gasp by the RBOCs and it is not going to work.” The main line of argument is that products like CellSocket will allow users to use excess minutes from their wireless plan but utilize the phones already installed at home. I am hesitant to argue against predictions and so I am not very much interested in the voracity of this prediction. But in subsequent posts, it was mentioned that CellSocket suggests that one can “cut the cord” to the phone company and use any phone at home to place a call over the cell phone; whereas none of the VoIP ATA vendors suggest that their devices could be used in such a fashion. No explanation will satisfy the original poster because no published information could be supplied. I would like to suggest to at least the readers of this blog that even the existing ATAs could be used in the same manner as CellSocket., even though it is not clear to me why none of the vendors say as much in their website.

Technically speaking, both CellSocket and ATA’s support FXS interface on the “line side”; that is they behave like a Class 5 switch, providing dial tone, collecting digits and generating ringing current. We just have to ensure that the telephone network’s Class 5 switch has been totally disconnected.

The following rationalization may appeal to some: ATAs allow for phones to be directly connected. There is no practical limit on the length of the wire between ATA and the phone. The length could be extended by coupling two wires. This is exactly the arrangement when the ATA is connected to a wall jack and the phone is connected to another jack in the house. We have to make sure ATA is the only source of power on the line. That is why we have to totally disconnect the service from the telephone company.

Posted by aswath at January 4, 2004 12:18 AM
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