Hi,
Direct Servo Control (DSC) allows you to control your servos from the transmitter without turning your transmitter on. This is done by supplying power through a special cable from the system to the transmitter which powers the CPU in the transmitter but not the RF deck. This allows you to setup your servos at the field without turning your transmitter on.

If you plug any of the pigtails into the battery slot of a JR receiver the receiver will go dead, it will not listen for the signal on the antenna but will look for an input signal through the DSC lead on the battery port. Plugging a pigtail into the battery slot of a 2.4GHz receiver will put it into bind mode and never let it out.