Connecting two ADSL modems

[#1]

Simple question.  What would happen if I were to connect a standard BT Voyager 105 modem at the same time as a separate wireless modem/ router to my ADSL line ?  In other words, I want to use the wifi router most of the time but for VOIP useage, I would prefer to use a hard-wired connection without having to climb under the desk to try to find the wifi modem / router.  It would be so much simpler just to have a second hard-wired modem available for the occasional use already plugged into another BT telephone socket which I could then connect with an ethernet cable to my laptop.
I don't want to go into all the why's and wherefore's - I know I could leave an ethernet cable connected to the router but it is in the wrong room for my purposes.  So I just want to use the Voyager 105 from time to time as a direct connection in another room.
Would the two modems fight with one another for priority and would I keep having to turn off the wifi router / modem before using the Voyager 105 ?  It would make life so much easier if I could just use two modems together.
I could try it and see of course, but it means installing the modem and then if it does not work, uninstalling it and I hate to upset my system unncessarily !
Thanks.

[#2]

You can only connect one ADSL modem at a time to an ADSL line.
You'd have to switch off whichever one you weren't using at the time.

[#3]

Having both connected simultaneously will probably also mess around with your sync speeds, so generally a bad idea

[#4]

What about using powerline ethernet adapters would enable you to plug in your other room without running masses of extra cable.

[#5]

Thanks chaps, that's the answer I feared !
I have been thinking of Home Plugs as siggested but they are expensive and the spare modem I have seemed like a cheap solution.  But I guess the only answer is Home Plugs.

[#6]

You might be able to configure your wireless router as an access point, in which case it just behaves like a network hub. The instruction manual should tell you if/how to do it.Your wired router would plug in to the phone socket,then you run a network cable from it to the wireless router.
If it won't do that, you could just buy a wireless access point which will achieve the same thing.