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Figure 1.3: The complete injection phantom

"... further flexibility is provided by an onboard audio oscillator microchip which produces quadrature phase audio signals. These may be fed directly to the mixers, allowing single frequency injection again at twelve distinct Doppler shift frequencies between 200 Hz and 14 KHz.

A single switch on the phantom front panel allows selection of either the onboard audio signal generator or an external signal source (passed through the audio phasing board), such as a cassette deck, for pre-recorded waveform injection."