The most common use of 3 wire control is a Start/Stop control. See image below for an example of 3 wire control being used to pull in a contactor to start a 3 phase motor. When you press the start button and the stop button is not pressed, the 24VDC relay energizes and it pulls in the R1 contactor that feeds three phase power to the motor.
2.Contact pulls in creating a parallel live supply 3.You take your finger off the spring return button Leaving only the contact live powering its own coil 4. you push the stop breaking the circuit. 5. Coil drops out meaning the emergency stop needs making n/c (resetting) and the start button pressing to remake the circuit. (back to top)
Adding a jog input to the hard wiring diagram will look something like this: You can see that the diagram will work the exact same as the circuit above with the start and stop pushbuttons. The jog when pushed will break the sealing contact, and then make a bypass of the start pushbutton.
Advantages of this circuit: In case of break in the cable or removal of any lamp will not break the all circuits, in other words, other lights/lamps will still work and glow. As more lamps are added, they will all be reduced in brightness. Because voltages is shared or divided in a series circuit. More size of cable wire is used in parallel lighting circuit wiring.
Motor Starter schematic and wiring diagram. Start stop 3 wire control. Starting a three phase motor.
More data would be needed for the start stop switch and/or if there is a relay in the junction box or seperate overload units. As a guess, without a relay, I would say 1-3 connect to 4-6 on the start switch, but 7-9 should come from the lower side of the start switch, only if it is 3 pole, single throw switch.