I considered using the power chair batteries but thenwas told if there was a heavy demand on the battery from the power chair it could effect the Vent. So the first one I did way back in the early '80s I made it so the chair battery was a reserve power for the Vent but cut the power to the chair when it happened. Now I just fit a rape alarm that the user could activate. On the assumption that they would always have some one near who could use the manual function. Michael Hare. Senior Rhabilitation Engineer. Wheelchair & Prosthetics Service. Chapel Allerton Hospital. Leeds LS7 4SA. Tel : 0113 3924981 Mobile : 07949 102232 email : [log in to unmask]