DTMFnäppäinvalintoja

DTMFnäppäinvalintoja, also known as Dual-Tone Multi-Frequency dialing, is a signaling system used to transmit telephone numbers and commands over analog telephone lines. It was developed by Bell Labs in the 1960s and replaced the older rotary dial pulse dialing system. The "DTMF" in the name refers to the fact that each digit or command is represented by a unique combination of two audio frequencies.

When a user presses a button on a DTMF-enabled keypad, such as a telephone or a softphone interface, the device generates a specific pair of tones. One tone comes from a low-frequency group, and the other comes from a high-frequency group. For example, the digit "1" is represented by the low-frequency tone of 697 Hz and the high-frequency tone of 1209 Hz. The combination of these two tones uniquely identifies the pressed digit or function key.

This system allows for faster dialing compared to pulse dialing. DTMF tones are also used for automated systems like interactive voice response (IVR) systems, where users input selections by pressing numbers on their keypad to navigate menus or provide information. The DTMF standard ensures compatibility across different telephone networks and devices, making it a ubiquitous method for command and control in telephony. It is also used in some wireless communication systems and specialized industrial applications.