The Mechanics of Analog and Digital Voice Circuits
In the previous section, you were introduced to analog and digital voice connections. Now, the material gets more specific and examines the electrical characteristics of these connections.
First, consider the following types of signaling that are present in the analog telephony world:
• Supervisory signaling—Indicates the on-hook or off-hook condition of a phone, based on whether loop current is flowing. In addition, “ringing” is considered to be supervisory signaling. Ringing voltage is sent from the phone switch to alert the destination phone that it is receiving an incoming call. In the United States, the pattern of ringing (that is, ring cadence) is 2 seconds on ...