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Modulation Fallback

What Does Modulation Fallback Mean?

Modulation fallback is a built-in modem feature that facilitates data connectivity and transfer between two modems operating at different maximum speeds. The highest common speed is the fastest data transfer speed between modems. This means that the faster modem must "fall back" to the speed of the slower modem.


Also, when a modem cannot connect with another modem for other reasons, such as changing line conditions, it will reattempt the transfer at a lower speed.

Techopedia Explains Modulation Fallback

During a modem call, the calling modem sends out a tone in a specific modulation that is often determined by the interface speed between the modem and its corresponding PC. If the answering modem supports the sent modulation, a connection occurs immediately. If not, the calling modem may have to fall back to the highest modulation that the two modems have in common.

Examples of modulation fallback for specific dial-up standards include:

  • V.22 modem: Actual rate: 1,200 bps; Fallback rate: 600 bps
  • V.22bis modem: Actual rate: 2,400 bps; Fallback rate: 1,200 bps
  • V.27 modem: Actual rate: 4,800 bps; Fallback rate: 2,400 bps

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