Actually live pto is controlled by the clutch. Independent pto has it's own clutch independent of the tranny clutch. . Another term for "live power" is "two stage clutch."
Sent from my iPhone using Tapatalk
That is perhaps a newer definition. When tractors first came out with the separate clutch on the pto, the were marketed as having "live pto and hydraulics"
On the older tractors without live power, the hydraulic pump was also driven off the pto shaft, meaning the hydraulics only worked if the pto was in gear and the tractor clutch was engaged. This didn't make for handy loader tractors, as you couldn't operate the hydraulics unless either the tractor was being driven, or you stopped and shifted the tractor into neutral, re engaged the clutch so the hydraulics could be used and then when ready, disengage the clutch, shift the tractor back into gear and re engage the clutch.
Any how on tractors with live power, the hydraulic pump is driven off the pto shaft internally before the pto clutch so it is driven constantly. Then the pto clutch turns the external pto shaft on or off independently. Of course some tractors have engine driven pumps, but they are usually smaller in capacity.
The newer differentiation of live pto and independent pto has been brought about since the development of the two stage clutches. But when the separate pto clutches were first introduced in the late 40's and early 50's, it was marketed as live pto on company literature and it is still very commonly used, although it certainly is independent as well.