Instruction manual

ACU-1000 Operations Manual
2-100 Interoperability Now
In the ACU-1000, DTMF detection is performed by the DSP-2 module rather than by the
associated receiver. When the DSP-2 receives line audio or speaker audio from an FM receiver
(rather than discriminator audio), any received DTMF characters have been inappropriately de-
emphasized. This incorrect shaping of the frequency response of the DTMF characters
impedes proper DTMF detection. The DSP-2 can add pre-emphasis to the DTMF detection
algorithm (leaving the received audio flat) for improved detection.
Note that these settings do not affect the audio that is passed on by the DSP-2 to be cross-
connected via another module in the system. The factory default adds pre-emphasis and should
be used any time the DSP-2 audio input source is the line audio or speaker audio output of an
FM receiver. The no pre-emphasis selection should be used if the audio source is the
discriminator output of an FM receiver or from a source other than an FM receiver.
2.17.2.17 Auxiliary Output Control
The standard configuration for DSP-2 is that the AUX-1 output changes logic state when the
module is cross-connected. Contact the factory if other configurations are required.
2.17.2.18 Voice Prompt Initiation Delay
A delay can be added to the onset of system voice prompts. Different delays can be added to
any of the interface modules. This variable delay is mainly used to compensate for slow-to-
react equipment associated with a module. For example, if a local radio associated with a DSP-
2 module has a long settling time after its PTT is activated, it may be necessary to delay all
voice prompts transmitted via the DSP-2. When additional delay is required, the distant radio
user will not hear the beginnings of system voice prompts.
The factory default for and DSP-2 modules is 100 ms; for PSTN-2, and LP-2 modules, the
default is no delay.