Instruction manual

ACU-1000 Operations Manual
Interoperability Now 2-27
If the radio Squelch Type is either COR or VOX, and the channel is noisy, the radio may
unsquelch inappropriately due to this RF noise. When the radio is cross-connected to another
radio via the ACU-1000 or ACU-T, the cross-connected radio will transmit every time the
noisy radio unsquelches.
If a radio has a tendency to key on noise, change the Squelch Type to VMR (Voice Modulation
Recognition). The DSP Module will unsquelch only when human speech is detected in the
receive signal.
[Inappropriate unsquelch of the radio can’t be resolved by changing the VOX Threshold of the
DSP Module]
(QA3 Yes) Set Squelch Type To VMR Mode
• On the DSP Module Settings Screen, select VMR from the Squelch Type options.
• Next determine the proper threshold. Listen while the radio receives a speech signal.
The default setting is Med1. If the radio does not break squelch for all received speech,
the threshold is too high; adjust to Low. If the radio breaks squelch on all speech
signals and also on some noise input, increase the threshold to the Med 2 setting, and if
necessary to High. (Note, for extremely noisy signals it may not be possible to find a
threshold setting that will unsquelch for all speech signals and also always stay
squelched during periods of high noise).
• Now adjust the hang time. The intent of VMR hang time is to keep the system
unsquelched during pauses in speech. The default (and minimum) setting is 775
milliseconds. If the radio squelches inappropriately during the reception of speech,
raise the hang time in one step increments until proper operation is reached.
• Click “Apply” to save the settings.
Jump to QA4
(QA3 No) Jump to QA4
QA4 Is The Radio Part of a Trunking System?
Trunked radio systems allow efficient use of multiple channel systems. When a user requests
access, the system automatically switches the user’s radio to a free (unused) channel. Trunked
systems users, when keying their radios, must wait for a tone that signals that a free channel has
been acquired before beginning a conversation, while conventional (non-trunked) system users
can begin talking as soon as they key their radios.
The “Channel Acquired Tone” that signals trunked radio users that they may begin speaking is
not available to system users on cross-connected radios, so the trunked radio’s TX audio must
be delayed, following assertion of PTT, until the normal channel acquisition time has passed.
(QA4 Yes) Jump to Flow Chart C
(QA4 No) Jump to QA5