rotary500

I have picked up a hitec phone which looks similar to the glx standard. Are these systems compatible, or do they use different voltages and/or wiring, sort of like the glx and look alike gmx phones which have no compatibility whatsoever? My house uses a GLX ksu and I am looking to add an extra extension by either adding a phone or locating an APM and using a single line set. Any ideas ( other than replacing everything )