Voice and Standards

Rotary vs. Dual Tone Multi-Frequency Dialing (DTMF)

Dual Tone Multi-Frequency (DTMF), also called “Touch tone”, was first introduced in 1963 by AT&T as a means for the central office to set up calls at a faster rate. Its roots are traced back to the 1950s when AT&T first developed a technique called MF (Multi-Frequency) which was first deployed within AT&T’s telephone network to direct calls between switching facilities using in-band signaling (Durda, 2003). Before DTMF’s introduction in 1963, most calls within the phone system were dialed using pulse signals, also called “rotary dialing”. This form of dialing used to take approximately 11.3 seconds to dial a 10-digit phone number using rotary pulses. When DTMF was introduced, a ten-digit phone number can be dialed within or less than a second. DTMF makes telephone communications more efficient because it resulted in faster call set-ups by the central office (Dodd, 1999).

Wide Area Telephone Service vs. Leased Lines

WATS (Wide Area Telephone Service) is a telephone service that offer fixed-rate long-distance phone service for businesses. This service allows the organization to pay a flat fee for most of its The three types of WATS lines are IN-WATS (incoming calls), OUT-WATS (outgoing calls), and the combination of both. IN-WATS is a telephone line that permits a customers to call toll-free to the organization who subscribes this service. Area codes such as 800, 888, and 877 are dedicated for this toll-free purpose. The people calling these numbers are not charged any long distance fees but the organization that has it is charged a fixed monthly rate. The other WATS line is the OUT-WATS lines, which are outgoing long-distance calling for organizations also charged at a fixed monthly rate (SearchSMB, 2001).

A leased line is an always-on dedicated telephone connection between two company locations. Leased lines are often utilized by organizations as a means to exclusively connect distant offices permanently. Just like the WATS, this service is available for a fixed monthly fee which depends on the distance and the speed of the circuit. Its use is basically limited compared to a WATS subscription because a leased line is only dedicated to the two locations, making it impossible to make or accept calls from other sources. WATS lines, on the other hand, are available for either incoming or outgoing calls, making it the smarter choice for businesses.

Private Branch Exchange (PBX) vs. Central Exchange (Centrex)

Most large businesses have their own phone switching machine called a Private Branch Exchange, or a “PBX”. These PBXes allow users