Some find unplugging a Castle controller from the Rx disrupts all their work. Many have asked for something like a Y connector that gives an open lead for easy Castle linking but a traditional Y harness doesn't work when the other branch of the Y is connected to an Rx. The signal line must be discoonected from the Rx.
Castle Quick Connect does just that. It detects the presence of a Castle Link adapter on the free lead and switches the controller's signal line from the Rx to the Castle Link. Easy as that!