Instruction manual

ACU-1000 Operations Manual
Interoperability Now 2-99
2.17.2.13 Module Security Level Selection
This command sets a module’s security level. Where n is the security level, with the security
level set by n defined as: 0 = not secure (no PIN required), 1 = least secure, up to 9 = most
secure.
2.17.2.14 DTMF Commands Enable/Disable
This configuration item determines whether an ACU-1000 module considers any DTMF
characters present in its input audio to be commands meant for that module.
When DTMF commands are disabled, they are not considered as commands to the receiving
module blocked from passing through the module. If the DTMF Mute Timer is enabled, the
DTMF characters are detected and muted. If the DTMF Mute Timer is disabled, any incoming
DTMF is simply passed through along with the rest of the program audio. A likely reason for
setting the module to the DTMF Command Disable mode would be to prevent any outside
users from connecting to the ACU-1000 system via DTMF. This is especially likely if an
operator using the ACU Controller software normally controls the system, and authorized
system users do not have DTMF keypads on their radios.
The default factory setting is DTMF Commands enabled. In this mode, the receiving module
assumes that all incoming DTMF characters are commands and responds accordingly. See
Section 2.17.2.5 for proper DTMF Mute Timer adjustment, and Section 3.5.1.9, which explains
the Data and Command modes, which can be used to temporarily (and remotely) control the
use of DTMF input, without having to enter the programming mode.
2.17.2.15 High Frequency Equalizer (DSP Only)
The DSP-2 module can reshape the high frequency response of it’s receive audio input.
Equalization can have two effects:
1. Improved DTMF detection when using radios with a nonlinear response, and,
2. Better-sounding audio for some radios. The high frequency response can be either cut
or boosted by up to 5 dB.
A flat frequency response is the factory default setting.
2.17.2.16 DTMF Pre-emphasis (DSP Only)
FM radios (VHF, UHF, 800 MHz) use pre-emphasis in the transmitted audio and de-emphasis
in the received audio. Pre-emphasis and de-emphasis alter, and then restore, the audio
frequency response in order to improve the quality of the received signal with respect to high
frequency noise. In most FM transmitters that have built-in DTMF signaling, the DTMF
characters are added after the pre-emphasis circuitry. When detected in an FM receiver, the
DTMF characters are taken from the discriminator audio, prior to the de-emphasis circuitry.