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21016 SMU1-MPAB3 V1.3.doc
control applied by the compressor so that an approximately constant level of
surveillance tone is always available at the output.
A chime circuit (ding-dong) may be optionally triggered from the control input
(e.g. Press to talk switch) and if used gives a logic level output which is
intended to flash an led during the chime and switch it continuously on when
the microphone is enabled.
Finally, the microphone is 'live' all of the time so as to enable continuous
surveillance of all of the circuitry in the system. However, to avoid audible
signal pick-up from the microphone in its non-active state, additional gain
reduction is applied in this state which is switched out when the microphone
is required.
A digitally synthesized 20kHz monitor tone for the Audix Systems FMS is
injected directly at the microphone head, with innovative circuitry able to
detect open or short circuit failure of the microphone.
The MPAB3 microphone pre amplifier features a choice of 2 built in pre
announcement chime signals. There is independent adjustment for the chime
volume.
Due to continued development, Audix Systems reserves the right to change
any of the operational features of the SMU1 described in this document.
