摘要 |
<p>A public address network includes a driver unit (11) that comprises a high pass circuitry pass and a low pass circuitry pass. The high pass part drives an audio signal (14) on to a pair of signal wires (12). The low pass part comprises a gyrator circuit that drives a pilot signal (15) on to the pair of signal wires (12).</p><p>The signal wires transmit the audio signal and deliver it to one or more audio output units (16). The signal wires also transmit the pilot signal and deliver it to one or more isolator circuits (20). Each isolator circuit is arranged to operatively isolate a section of the signal wires.
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