7 recommended by CCITT has been widely used in the digital telephone switching network and in the coming ISDN because of its high efficiency, flexibility and versatility.

• 7公共信道信令系统(CCSS),由于它的高效率、灵活性和多用性,已广泛地用于数字电话交换网和即将到来的综合业务数字网(ISDN)中。