A board from another developer uses a three-pin connector. This is a very simple and inexpensive solution. The pin-out of the connector is shown below.

1. GND - the ground for power and signal
2. +24V - the power for the servomotor
3. DIR - the direction signal: 0 - rotate CW, 1 - rotate CCW

The motor stops by itself when the marker reaches the optical sensor.

The disadvantages of this are:

• The control controller has no status from the servo motor;
• If the device is suddenly de-energized, the servo motor will start moving in the default direction when power is restored. This somewhat makes the process of powering up the device a bit daunting for the user

Solution 1 - With RS485

For more complete control you can use RS485 interface. Then there will be a pinout.

1. GND - power ground
2. +24V - power
3. A - RS485
4. B - RS485

However, this will require a microcontroller and interface converter to be installed on the board. This makes the construction more expensive.

Solution 2 - With I2C

It will be a little cheaper if you use I2C interface.

1. GND - power ground
2. +24V - power 
3. GND - signal ground
4. SCL - I2C
5. SDA - I2C

Solution 2 - Passive

In this case only the motor driver is installed on the board. Then the pinout will be as follows.

1. GND - power ground
2. +24V - power
3. GND - signal ground
4. M1 - motor in1
5. M2 - motor in2
6. S1 - sensor 1
7. S2 - sensor 2

Conclusion

Tough choice considering the connectors and wires cost their money too. However, the RS485 option looks like the most noise-protected and therefore reliable option.