Signaling is the process of exchange of information between the components required call for providing and maintaining services. For example: PSTN signaling between the user and the network including PSTN, to dial digits, providing a dial tone, voice mailbox access, send a call waiting tone to dial * 66 to repeat the number is busy, etc.. SS7 is a way in which telephone network elemen2 exchange information. This information is presented in the form of message. Overview: SS7 signaling system is the primary signaling system for the PSTN and PLMN. SS7 defines the procedures set up, manage and cut communication between users as well as non-circuit signaling. SS7 (Signaling System 7) is an architecture organizer "out of band signaling" in supporting the stability of calls, billing, routing, and function of a network exchange of information with PSTN (Public Swithing Telephone Network). Definition of "Out of band signaling" Out of band signaling is signaling that are not placed in the paths equal to the line of conversation. The traditional signaling condition, namely before the conversation begins signaling (exchange of information) will occur through the same path with the path that eventually will be used to pass the conversation. So early to hear a dial tone, dial digits and hear ringing through the same channels on the same wire pair. So the signal to setup a call between a switch with other switches will always occupy the same trunk with the trunk that will eventually bring traffic conversation. Out of band signaling that stabilizes a separate digital channel (digital channel separated) to exchange signaling information is also called signaling links. Signaling links are usually used to carry all the necessary signaling message between node2. Thus, if there is a call, didial digits, trunk selected, and other important informasi2 sent between switches using trunk signaling link while the later will be used to carry the traffic conversation. We signaling links carry information at speeds of 56 or 64 kbps. Interesting to note that while SS7 is only used for signaling between network elements, ISDN D-channel to develop the concept of out of signaling to the interface between the subscriber with a switch. Through the ISDN service, which must be submitted signaling between MS with the local switch is carried by a separate digital channel called channel D. whereas for voice and data traffic carried by one or more channel B.