Is there a 3.5mm headset jack to RJ11 plug adaptor device?

[TTCP]

I know OBI 200/202 + OBI BlueTooth device can link a cell phone to the OBI unit. But BlueTooth kills cell phone battery in big way.

Since all cell phones have 3.5mm headset jack, I am wondering whether there exists a 3.5mm headset jack to RJ11 plug adaptor device, that I can use to plug into the cell phone headset jack, and the other end plug into an OBI 110 Line Port. So when there is an incoming cell phone call, the audio stream is be redirected to the OBI 110 Line Port, then I can do whatever clever things I want with some inbound call route.

If there exists such a device, then I personally believe it is better than the OBI BlueTooth device, as it does not consume cell phone battery at all, and also I do not have to constantly turn on and turn off cell phone bluetooth. ( I know with this set-up, I cannot make outgoing calls via OBI 110 Line Port. But I am OK with it. )

[SteveInWA]

No.  They are entirely different interfaces in every way.

[drgeoff]

Among the many differences:

A headset jack has separate wires for the mic and earphones.  It has no signalling - you cannot dial  using it.

The OBi LINE jack, has send and receive audio on the same wires.  It accepts DTMF dial tones.  It expects 48 volts DC fed into it.  It understands that 80 volts AC coming in means it is being rung.  It understands Caller ID.

So it not just a case of the connector being different.  By the time you have added all the electronics needed to cater for the above, you have built more than half of an OBi110.