all-trac design question

does anyone know the how the design of the all-trac works? i bought this old 88 camry with the differintial lock servo i'll call it taken off. the previous owner thought it was in all wheel drive at the time. well i was able to move the all-trac engagement shaft today thinking i was putting it in just two wheel drive but it must of put it in all wheel as it was difficult to turn. now i guess my question is . are these allwheel drive all the time and the differintial lock is for locking up both the front and the rear?or is it normally just front wheel drive untill the differintial lock button is engaged. also i'm still trying to sort out the vacuum hose routing from the elec/ vac switch to the servo if anyone has a diagram to it. thanks..............steve