e used in the core, or backbone, net- work-51Mbps is considered the starting point for broadband. In the wireless realm, though, if we could get 2Mbps to a handheld today, we'd be extremely happy and would be willing to call it broadband. So remember that the definition Chapter 1 Telecommunications Technology Fundamentals of broadband really depends on the situation. But we can pretty easily say that broadband is always a multichannel facility that affords higher capacities than the traditional voice channel, and in the local loop, 2Mbps is a major improvement. Analog and Digital Transmission There are a number of differences between analog and digital transmission, and it is important to understand how conversions between analog and digital occur. Let's look first at the older form of transmission, analog. Analog Transmission An analog waveform (or signal) is characterized by being continuously variable along amplitude and frequency. In the case of telephony, for instance, when you speak into a handset, the air pressure changes around your mouth. Those changes in air pressure fall onto the handset, where they are amplified and then converted into current, or voltage fluctuations. Those fluctuations in current are an analog of the actual voice pattern-hence the use of the term analog to describe these signals (see Figure 1.9). When it comes to an analog circuit-what we also refer to as a voice-grade line-we need to define the frequency band in which it operates. The human voice, for example, can typically generate frequencies from 100Hz to 10,000Hz, for a bandwidth of 9,900Hz. But the ear does not require a vast range of frequencies to elicit meaning from ordinary speech; the majority of sounds we make that consti- tute intelligible speech fall between 250Hz and 3,400Hz. Therefore, the phone company typically allotted a total bandwidth of 4,000Hz for voice transmission. Remember that the total frequency spectrum of twisted-pair is 1MHz. To provision Voice Pattern Analog Wave Form Figure 1.9 Analog transmission An