The SQ-1 Y-Cable is a Futaba F-M-M Configuration that splits any receiver channel into two connectors. So, the SQ-1 Y-Cable allows the SQ-1 to get power and signal off the Motor Port of your receiver. One leg of the SQ-1 Y-Cable is shorter than the other. Connect your motor servo to the short leg, so they can both live inside your receiver box. The longer leg this where you plug the SQ-1 into, and this leg is meant to be run outside of the receiver box so that you can easily connect to the SQ-1.
The SQ-1 Y-Cable can be used with any device that you need to tap into signal and power from your receiver.
The SQ-1 Y-Cable taps power and signal to your SQ-1 from your receiver's motor port (normally Channel2 on your Receiver). The SQ-1 Y-Cable is is designed so that one leg of the cable is connected to your motor servo cable and stays inside your receiver box. The other output leg connects to your SQ-1 and should be run outside the receiver box so that you can easily connect and disconnect your SQ-1 to your vehicle.