Cs for long distance, interna- tional carriers for overseas calls, mobile providers, and ISPs. Services Beyond the Local Loop Traditionally, we have thought of the local loop as leading to the home or to the business and ending there. But the need for additional bandwidth and capability is now shifting: We need these things within the premises as well as on the local loop. It is therefore a log- ical extension for the service provider to not only give the customer access lines and ter- mination but also to provide the home area networking facilities needed for the customer to have an end-to-end broadband package. Chapter 12, "Broadband Access Alternatives," talks more about home area networking. The underlying network access facilities can be either analog or digital loops, and they connect the exchanges to the customer premises. At the customer pre- mises there are the network interfaces, customer premises equipment (CPE), premises distribution systems where wiring is cross-connected, and network interfaces. The equipment for providing switch access services includes line-termination cards, carrier and multiplexer equipment, and local exchange switching capabili- ties that support addressing, supervisory alerting, call progress, and other signal- ing functions. Access Services The main categories of access services are trunks, business lines for key telephone systems, centrex service, leased lines, and residential subscriber lines. Chapter 4 The PSTN Trunks are used to provide connections into the PBX environment. There are three subcategories of trunks: Two-way local exchange trunks-On these trunks, traffic flows in both the incoming and outgoing directions. DID trunks-Direct inward dialing (DID) trunks are designed for only incoming calls. A benefit of DID trunks is that they enable the dialed num- ber to ring directly on a user's phone rather than having to go through a centralized attendant, with the connection being established within the PBX switch. If people know whom they want to call directly, this can 