Week 1 Exercise 1

Fixed Line telephones have been around since 1877 with the formation of the Bell Telephone Company. These phones were originally not made to be connected to more than one phone at a time. As the phone system advanced, fixed line telephones were all connected together through a central office. A local loop connects a house (subscriber) to the central office. A local loop is made up of a twisted pair of copper cables and has a maximum length of three miles. Being made up of these pair of copper cables gives the local loop the nickname “twisted pair.” A central office serves subscribers in a local area. Each central office has its own three digit code that is the first three digits of the phone number given to each subscriber. The last four digits in a subscriber’s phone number is unique to that subscriber. Ranging from 0000 to 9999, one central office can support up to 10,000 subscribers. Central offices can also be referred to as a local exchange. Many central offices can support more than one local exchange, some as many as twenty. Trunks connect central offices to each other and to local exchange carriers. Local exchanges are local telephone companies which provide service within a designated geographical area, or local access and transport area (LATA). A local exchange serves more than one central office. The higher the population, the more LATAs it takes to serve subscribers. Pop, or point of presence, is where a local exchange carrier or long distance carrier meets another long distance carrier. This provides the interconnection to the long distance carrier or inter-exchange carrier (IXC). In the U.S., Inter-exchange carriers provide long distance service. The Inter-exchange carriers are used by connecting local exchange carriers together in different LATAs or within the same LATA. This makes is how the long distance