Rotary and Dual Tone Multi-frequency (DTMF)Telephone communication is designed to create a circuitous route between two callers and subsequently between two telephones. Call routing is determined using one of two methods, pulse or rotary dialing or dual tone multi-frequency (DTMF).
Macao Communications describes pulse dialing by using the following example,While Dialing a Number, for example, five, the Dial is drawn round in the Clockwise Direction to the Finger Stop Position and released. The ICT [phone] then generates the Dial Pulses by closing and opening itself to interrupt the DC Current loop. The number of interruptions is equivalent to the Dialed Digit. After finishing Dialing, the Pulses are then decoded at the Telephone Exchange that makes a connection to the Called Customer (2008).
As noted previously call routing is the goal and instead of the electronic pulses used in rotary dial telephones, DTMF uses sound tones to determine the call route. In fact, each button on a touch tone telephone generates a pair of tones (hence the name dual tone). Each pairs of tones consists of a high frequency and low frequency tone as illustrated in the chart below.
The combination of the tones, along with the order they are selected is then decoded in the same way the rotary dial is and the call is routed to the appropriate receiver. DTMF is far more accurate than rotary dialing because the combination of tones and their sequence determines the opening and closing of the circuit. In contrast, rotary dial phones rely on the number of clicks or circuits passed as the rotary dial spins past. If the user does not fully reach the number five the number of clicks will be off. Similarly, these electronic circuits are subject to interference and ultimately misinterpretation. The efficiency of DTMF compared to rotary dialing has made the rotary dial phone obsolete.
Wide Area Telecommunications Service (WATS) and leased linesWide Area Telecommunications Service gained popularity in the 90s as deregulation spawned competition between telecommunications companies. Until this point, most customers were charged per call. The advent of WATS, which is primarily a billing system, provided customers with per use service as opposed to per call. Customers are not billed per call, but by the number of hours, they have purchased. In addition, overtime is charged at a reduced rate.
Leased lines are direct telephone lines between different offices or buildings...