Although DTMF works in normal human voice range, the combination of inharmonic frequencies makes it hard for the human voice to impersonate.Īlthough mobile phone networks use digital signals instead of DTMF for direct dialing, DTMF is still used over mobile phones to navigate automated systems such as phone menus, voice menus and other advanced calling services. The frequencies were chosen to avoid harmonics : no frequency is a multiple of another, the difference between any two frequencies does not equal any of the frequencies, and the sum of any two frequencies does not equal any of the frequencies. Results of 2-tone IMD tests can be found in every ARRL review of new transceivers and power amplifiers. This type of testing is most commonly used as a measure of transmitter linearity for amateur radio equipment. This Two Tone test generator provides a standard 2-tone (7 Hz) audio source. With DTMF, each keypress on your phone generates tones made of two specific frequencies. Figure 1 The TTG1 Two Tone test generator Fig 1. Over the years, DTMF has replaced Pulse dialing, the early type of telephone dialing in which short pulses were used to relay the dialed number. While the dark fiber can be identified using a tone generator (270 Hz, 1 kHz, 2 kHz), the live fiber identification technique often involves one technician pulling one end of the patchcord, with another technician trying to identify which patchcord is moving at the other end-a process that translates into long delays and can result in unnecessary service disruption.Ĭombined with the TG-300B Tone Generator, the innovative LFD-300B FiberFinder™ Live Fiber Identifier enables technicians to identify a specific live fiber without having to disconnect it and, above all, without having to guess.Dual-Tone Multi-Frequency (DTMF) is the signal that you generate when you press an ordinary telephone's touch keys. The Test Tone Generator (TTG) turns the PC into a function generator for testing or demonstration, sound tuning, education or for sound effects. This is often easier said than done, since finding the right connection can be tricky, namely because of fiber mislabeling or poor record keeping. Performing network upgrade or optical testing requires a fiber to be disconnected. Pinpointing live and dark fibers: guesswork ends here
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