Common POTS Terms

Question 1

Telco

Answer 1

Telco A telco is a telephone company. Some countries have government-maintained telcos, whereas
other countries have multiple competitive telcos.

Question 2

Local loop

Answer 2

Local
loop
A local loop is a connection between a customer’s premises and their local telephone central
office (CO).

Question 3

Central

office

Answer 3

Central
office
(CO)
A building containing a telephone company’s telephone switching equipment is referred to a
central office (CO). COs are categorized into five hierarchical classes. A Class 1 CO is a
long-distance office serving a regional area. A Class 2 CO is a second-level long-distance
office (it’s subordinate to a Class 1 office). A Class 3 CO is a third-level long-distance
office. A Class 4 CO is a fourth-level long-distance office that provides telephone
subscribers access to a live operator. A Class 5 CO is at the bottom of the five-layer
hierarchy and physically connects to customer devices in the local are

Question 4

Tip and

ring

Answer 4

Tip and
ring
The tip and ring wires are the red and green wires found in an RJ-11 wall jack, which carry
voice, ringing voltage, and signaling information between an analog device (for example, a
phone or a modem) and a telephone’s wall jack.

Question 5

Demarc

Answer 5

DemarcA demarc (also known as a demarcation point or a demarc extension) is the point in a
telephone network where the maintenance responsibility passes from a telephone company to
the subscriber (unless the subscriber has purchased inside wiring maintenance). This demarc
is typically located in a box mounted to the outside of a customer’s building (for example, a
residential home). This box is called a network interface device (NID).

Question 6

Smart

jack

Answer 6

Smart
jack
A smart jack is a type of network interface device (see the definition for demarc) that adds
circuitry. This circuitry adds such features as converting between framing formats on a digital
circuit (for example, a T1 circuit), supporting remote diagnostics, and regenerating a digital
signal