CushionTheBlow (구 BluemoonSoft)

Customer-premises equipment or customer-provided equipment (CPE) is any terminal and associated equipment and inside wiring located at a subscriber's premises and connected with a carrier's telecommunication channel(s) at the demarcation point ("demarc"). The demarc is a point established in a building or complex to separate customer equipment from telephone company equipment.

CPE generally refers to telephones, DSL modems or cable modems, or purchased set-top boxes for use with Communications Service Providers' services. Also included are key telephone systems and most private branch exchanges. Excluded from CPE are overvoltage protection equipment and pay telephones.

Cellular carriers may sometimes internally refer to cellular phones a customer has purchased without a subsidy or from a third party as Customer Provided Equipment.

It is also notable that the Fully qualified domain name of DSL and cable lines connected to a residence will often be prefixed with 'cpe'.

Reference:
http://en.wikipedia.org/wiki/Customer-premises_equipment

A key system or key telephone system is a multiline telephone system typically used in small office environments.

Key systems are noted for their expandability and having individual line selection buttons for each connected phone line, however some features of a private branch exchange such as dialable intercoms may also commonly be present.

Key systems can be built using three principal architectures:

Electromechanical shared-control
Electronic shared-control
Independent keysets

Reference:
http://en.wikipedia.org/wiki/Key_telephone_system