We start from analyze of water wheel – well known and very old prime mover in the hydro power engineering. Traditionally water wheel is considered as one of the six simple machines, however the father of kinematics – Franz Reuleaux identified a lever, pulley, and wheel and axle are in essence the same device: a body rotating about a hinge.
Really, we can consider water wheel as the system of rotating levers (accordingly to each bucket of wheel at least) with common pivot at each moment of rotation – shaft of wheel. Depending on type of water wheel just part of buckets (roughly mo more than 25%) are contacting with moving water (as working medium) the rest (about 75%) are rotating by inertia, but losses (dissipation) are acting continuously. Note also that water wheel is not able to multiply the input force, but just converts it in output torque on the shaft of rotation.
Now, we can replace that system of rotating levers by one rocking symmetrical lever (or rocking beam) with two buckets on the opposite ends and with pivot in the centre of the shaft – it will be our first innovative step.
In this configuration the rocking beam can perform reciprocate motion in vertical plane and can be connected directly (by very simple linkage as connection rod) to the useful load with the same reciprocate nature of motion (piston pump, for example). The important fact is needless of any intermediate mechanism (gear, crank shaft, etc), which means the increasing of efficiency in the energy transforming. Again we can find evidence of this conclusion in the following quote:
“ … Every transmission or transformation of energy entails a loss, hence, starting with a given quantity of energy, it gradually dis- appears through the various losses involved in the mechanism or machines used. Other things being equal, the simpler the trans- mission or transformation, the greater the quantity of the original amount of energy that can be utilized. …” 
Moreover, we can add that similarity of nature of motion between prime mover and mechanical load is the main criterion in the effective their compatibility (as combination of simplicity and efficiency)
“… other losses depend both on the nature of the working medium (water, air, steam or electric current) and on the design, construction, maintenance and conditions of operation of the machine …” (prime mover, evidently – A. Kornich).
In other words we can see here some analogue of matching “mechanical impedance” from electrical engineering to maximize the power transfer.
” … It is therefore obvious that it is usually desirable to so select, install, maintain and operate machinery that it may work as nearly as possible with the least comparative losses or under the most efficient conditions …” (underlined by A.Kornich)
It is becoming clearer why the design of original water powered prime mover is so desirable: having various kind of output mechanical motion they could be connected to mechanical loads with particular similar motion more easily and effectively.
However, to provide the reciprocating motion of rocking beam in vertical plane we need to switch by alternately the flowing mass between buckets on the opposite ends of beam.
Logically, it can be done by another symmetrical rocking lever which is placed above of the main rocking beam and it has the fulcrum on the same vertical axis of mechanism. This “feeding lever” should be performed as pipe or narrow tray with attached intake assembly in the centre in such a way, that it will be capable to deliver the moving mass to the bucket of main beam in its high position accordingly.
The usage of rocking “feeding lever” in the kinematic scheme of original mechanism – it will be the second innovation step.
The next step of design is the right switching of “feeding lever” what means to direct of flowing mass only in that bucket of main beam which is in high position at the moment of operating of machine. Logically, it can be done if “feeding lever” and main beam are rocking in the “anti-phase”: when right arm of “feeding lever” is in low position (and provide the direction of flowing mass “to-the-right”); the left arm of main beam should be in low position (hence, the right arm of main beam will be in high position accordingly) for receiving of flowing mass in its higher bucket.
Due to symmetrical structure of machine the same picture we will have for left arms of rocking levers.
This requirement will be satisfied if we apply two symmetrical “mechanical feedback” crosses type: by mechanical linkage (hard or flexible) which connect left arm of main beam with right arm of “feeding lever” and contrariwise (see Fig. DPC1)
This symmetrical “mechanical feedback” – it will be the third innovation step.
Why we can talk about feedback effect in DPC machine?
This conclusion can be derived from operating regime of mechanism: when full bucket of main beam is driven down by gravity force (stroke of mechanism) and is capable to perform some mechanical work; some part of input energy is used (by pulling of cross type linkage) for the switching of direction of flowing mass and prepare in such a way the next symmetrical stroke of mechanism.
As result we can obtain the endless (in terms of potential of input energy) periodical consequence of strokes in machine, so oscillating mode of DPC can be realized. Similar action of feedback is basic principle for any oscillating generator (like electrical, for example).
Actually, the mechanical oscillation mode (provided by “mechanical feedback”) is the most distinctive feature of DPC machine as innovative prime mover which could be powered by gravity force of flowing mass.
Thus, in addition to practical use machines to perform various mechanical works, kinematics of DPC demonstrates the unity of principles of the feedback action with regard to input power (mechanism or electrical device) to generate a sequence of impulse actions such as electrical (pulses) or mechanical (strokes) nature. That the theory electro-hydraulic analogy can be complemented with another convincing example.