Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. In telephony, the local loop is the physical link or circuit that connects from the demarcation point of the customer premises to the edge of the carrier or telecommunications service provider''s network. At the edge of the carrier access network in a traditional PSTN scenario, the local loop terminates in a circuit switch housed in an ILEC CO. Traditionally, the local loop was wireline in nature from customer to central office, specifically in the form of an electrical circuit provisioned as a single twisted pair in support of voice communications. Where the number of local loops was restricted, different customers could share the same loop, known as a party line. Modern implementations may include a digital loop carrier system segment or fiber optic transmission system known as fiber-in-the-loop. The local loop may terminate at a circuit switch owned by a CLEC and housed in a POP, which typically is either an ILEC CO or a "carrier hotel". A local loop may be provisioned to support data communications applications, or combined voice and data such as digital subscriber line.