MultitoneSignalen

MultitoneSignalen, often referred to in English as multitone signaling, is a signaling technique in which information is conveyed by a set of simultaneous audio frequencies. In telecommunication, it is used to transmit control signals or data along a voice channel without relying on separate (out-of-band) signaling paths. A key characteristic is that each symbol corresponds to a distinct combination of frequencies, allowing relatively high information density on a narrow channel.

One of the most common forms is Dual-Tone Multi-Frequency (DTMF), used on touch-tone telephones. DTMF encodes digits and symbols by pairing one low-frequency and one high-frequency tone, producing eight frequencies in total. Other forms, historically known as multi-frequency (MF) signaling, were used in older telephone networks to transmit control digits via tone pairs.

Implementation typically relies on generating a fixed set of base frequencies and detecting the presence of these tones with filters or digital signal processing. The receiver identifies a symbol by detecting which frequencies are present and to what amplitudes. The approach is relatively cheap to implement, can operate over existing speech paths, and is robust to moderate noise and distortion. However, it has limitations: symbol rate is limited by the need to separate tones in frequency, it is susceptible to interference from strong tonal audio or harmonic distortion, and security concerns can arise if tones are easily spoofed.

Uses and applications include user input for IVR systems, remote control of equipment, and legacy signaling in telephone networks. With the advent of digital signaling protocols (for example, SS7) and data channels, multitone signaling is less central in modern core networks but remains in consumer devices and certain industrial systems.