Chapter 12Telecommunication Systems.ppt

Chapter 12 Telecommunication Systems Data Communications and Computer Networks Chapter 12 T-1 Service A T-1 service is a digital, synchronous TDM stream used by businesses and telephone companies. A T-1 service is always on and always transmitting. One T-1 service can support up to 24 simultaneous channels. These channels can be either voice or data (PBX support). A T-1 service can also be provisioned as a single channel delivering 1.544 Mbps of data (LAN to ISP connection). Data Communications and Computer Networks Chapter 12 T-1 Service A T-1 service requires 4 wires, as opposed to a 2-wire telephone line. A T-1 can be either intra-LATA (local) which costs roughly $350-$400 per month, or inter-LATA (long distance) which can cost thousands of dollars per month (usually based on distance). A customer may also be able to order a ? T-1 or a ? T-1. Data Communications and Computer Networks Chapter 12 T-1 Service A T-1constantly transmits frames (8000 frames per second). Each frame consists of one byte from each of the 24 channels, plus 1 sync bit (8 * 24 + 1 = 193 bits). 8000 frames per second * 193 bits per frame = 1.544 Mbps. If a channel is used for voice, each byte is one byte of PCM-encoded voice. If a channel is used for data, each byte contains 7 bits of data and 1 bit of control information (7 * 8000 = 56 kbps). Data Communications and Computer Networks Chapter 12 Integrated Services Digital Network (ISDN) ISDN is another leased service that provides a digital telephone or data connection into a home or business. With ISDN you can have a digital telephone line and a 64 kbps data line, or one 128 kbps data line. The basic rate interface (BRI) is the service for homes and small businesses, while the primary rate interface (PRI) is the service for larger businesses. Data Communications and Computer Networks Chapter 12 ISDN BRI ISDN c