Plain Old Telephone Service

Standard telephony service is commonly referred to as plain old telephone service (POTS). This service provides a dial tone to rotary and touch-tone telephones, as well as access to national and international carriers. Standard dialing devices such as 500-type telephones (rotary), 2500-type telephones (touch-tone), facsimiles, and modems are compatible with POTS.

POTS evolved internationally to include the 911 emergency number service and operator services. The following additional features and services are now almost universally available to POTS subscribers:

• Custom calling features

• Custom Local Area Signaling Service (CLASS) features

Each feature is discussed in more detail in the following sections. Custom Calling Features

The services available from custom calling features have been popular since they were introduced in the PSTN. Although you can activate and use each function individually, SPs usually combine features in a single package for simplicity and convenience.

You enable and control custom calling features from within end office switches directly. Signaling System 7 (SS7) messaging and service enablers are not required operate these features. The following list describes some common custom calling features:

• Call forwarding—Enables calls to follow as the subscriber moves from one location to another

• Call waiting—Indicates an incoming call when the subscriber is already involved in a call

• Three-way calling—Enables subscribers to conference a third party in on a conversation

• Speed dialing—Provides a convenient way for subscribers to store frequently used numbers

• Added number—Enables subscribers to add a second line that they can identify by a distinctive ring and call-waiting tones

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