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Now back to your home telephone and POTS. Prior to an advancement known as DTMF, telephones used '''rotary dial'''. Rotary dial telephones used signaling technology or pulse dialing. The numbers on a rotary dial phone are arranged in a circular layout so that a finger wheel may be rotated with one finger from the position of each digit to a fixed stop position. The mechanical signaling is accomplished as the wheel returns interrupting the direct electrical current of the telephone line (local loop) a specific number of times for each digit.Touch-tone land-line phones began to replace rotary dial. Bell Telephone introduced Touch Tone dialing in 1963 using the DTMF standard. '''DTMF''', or Dual Tone Multi-Frequency, is used when pressing a numbered key on the telephone dial pad. A specific DTMF tone is generated for each numbered key. The land-line phone system can then "listen" and decode that tone to determine which key was pressed, enabling dialing. Each DTMF "tone" is actually two tones - a low-frequency tone and a high-frequency tone - combined. (Hence the name "dual tone multi-frequency".)