Information Technology Reference
In-Depth Information
Figure 1-2
Electrical Analog Waveform of Human Speech
Note:
The analog waveform shown in Figure 1-2 is from me (Jeremy) saying, “Hello.”
Analog phone lines use the properties of electricity to convey changes in voice over ca-
bling. Of course, there is far more than just voice to send over the phone lines. The analog
phones you use at home must convey many different types of signaling, too. Signaling in-
cludes messages such as dial tone, dialed digits, busy signals, and so on. These signaling
types are discussed in just a moment. For now, let's look at the cabling used to make ana-
log connections function.
Each analog circuit is composed of a pair of wires. One wire is the ground, or positive
side of the connection (often called the tip). The other wire is the battery, or negative side
of the connection (often called the ring). You'll commonly hear phone technicians talk
about these wires as the “tip and ring.” These two wires are what power the analog phone
and allow it to function, just like the wires that connect your car battery to the car. Figure
1-3 illustrates the connections of the tip and ring wire to your analog phone.
Key
To p i c
Ground (tip)
Battery (ring)
Phone Company
Central Office
Analog Phone
On Hook
Phone
CO
Open Circuit
X
-
48 VDC
Figure 1-3
Connections of the Ground and Battery Wires to an Analog Phone
