Practical Asterisk 1.4 and 1.6: From Beginner to Expert

8. Making Connections

Asterisk finds its real power when you connect it to other systems, telephone devices, and networks. It accomplishes this through audio codecs and a variety of transport media, such as digital trunks (T1, E1) and traditional analog lines. In this chapter, we look more closely at codecs, ISDN, and analog telephony.

8.1 Codecs

A discussion of codecs, as they are used in telephony, will put someone on one of two sides of a large mountain. On one side of the mountain, we have the situation in North America, which has very little ISDN penetration, at least at the retail level. The average North American telephone customer has only ever used analog telephones, and so the stack of digital codecs is seen from the base of a mountain ...