Modem to Modem without a line simulator?

This question is bugging me from another forum. Is it possible to connect two modems (eg: Hayes 2400 to Hayes 2400) using a 'dead' or isolated pair of copper wire and have them be able to communicate? I always thought that this can not work because the line that the modems are connected to has to have some current. The phone system works because an action on one end of the phone (talking into the carbon microphone) causes a reaction on the other end. Without some sort of current on the line, how can this work? Hence the need for 'line simulator' circuits Some people are claiming that it works without the line simulator. I'd like to understand why. (I could get out the multimeter if things get really desperate, but maybe somebody can tell me that the line current thing only applies to acoustically connected modems, not direct connect. Or the direct connect modems put enough juice on the line to make it work. Or something else that might make sense.)