Instruction manual

ACU-1000 Operations Manual
Interoperability Now 2-95
reliably detected under most conditions. The VOX detection time is normally just a few
tens of milliseconds, so its default delay time is 60 msec. The delays should be kept at the
default values unless some system requirement dictates a change, such as the use of slow-
to-key radios.
Be advised of the following important characteristics of the RX audio delay:
• There can never be a true “zero delay” for receive audio passing through the DSP-2
module; an inherent processing delay is always present.
• The RX audio delay does not delay the handling of the COR signal. This means that if two
radios are cross-connected through a pair of DSP modules, an active COR at one module
will immediately key the other module. The incoming RX audio will then be delayed from
being retransmitted at the connected module by the set RX audio delay time. The duration
of the COR signal (and corresponding PTT signal) will be extended by the set RX audio
delay time.
• Keep the delay set as low as possible for clarity of conversation. If the first syllable or part
of the first syllable is lost after a message is passed through the unit, most likely the audio
delay should be increased.
• Due to the longer processing time required for VMR mode, multiple keypad settings
(settings of 0 through 5) all set the delay to 220 ms. The longer input audio delays of 260
and 300 ms can be set with inputs of 6 or 7, respectively.
2.17.2.6.2 Transmit (Output) Audio Delay
The DSP-2 can also add delay to the audio output of the module. (See also Section
2.10.4.3. and Section 4.2) Transmit Audio Delay is mainly used when the 4-wire device
associated with the DSP-2 is a trunked radio. When a user makes a trunked system
transmission, there is a delay between when the radio’s PTT is activated and when a
channel is assigned so that communication may begin. Most trunking systems signal this
ready status by a confirmation tone. There is no means to transfer this tone to ACU-1000
system users who are cross-connected to the trunked system. Instead, the DSP-2 Output
Audio Delay should be set to a duration that holds the TX audio until the channel has been
selected so that the first syllable is not clipped.
Note that when two radios are cross-connected by a pair of DSP-2 modules, the RX (input)
audio delay of the receiving module is added to the TX (output) audio delay of the
transmitting module (assume to be a trunked radio). This occurs because, while the RX
audio is delayed by the set amount, the COR input takes effect immediately (see above).
This undelayed COR will immediately send an active PTT (via the cross-connected DSP-2
module), to the trunked radio. The audio from the receiving module is then sent to the
trunked radio delayed by the sum of the receiving module’s RX audio delay and the
transmitting (trunked) module’s TX Audio Delay. This provides a maximum total delay of
1100 milliseconds. If additional TX Audio Delay is required, contact the Raytheon factory
for recommendations.