The red plug of TEU101BK needs to be pluged into the BEC socket of the receiver so that the regulation circuit can reduce the voltage to an appropriate value for the receiver and servos as well. [i.e. your receiver have to be equipped with BEC, otherwise, don't use TEU101BK]
If you plug it to ch 3, the battery voltage (usually 7.2v) will then be directly feeded to the receiver and other servo. They may be damaged by the high voltage.
Other "better" ESC have built-in BEC to provide power to receiver so that it won't come with a "red plug".