LBI-39101
7
Digital Pots Settings
To provide computer-controlled level settings, the
Enhanced Audio Enclosure's audio input and audio output
circuits incorporate 256-position digitally-controlled
potentiometers. These digital pots, located on the Audio
System Board, allow adjustment of the Enhanced Audio
Enclosure's audio levels via the PC. Adjustments include
dispatcher-adjustable audio levels such as headset sidetone
volumes and system-level adjustments such as line input
and output levels to and from the CEC/IMC Digital Audio
Switch.
With the exception of the dispatcher's headset sidetone
volume adjustments, none of the digital pots provide
volume adjustments for the speaker or headset earphone
audio levels during normal dispatch operations. Speaker
and headset volume adjustments are accomplished at the
respective speaker or headset via mechanical pots.
Communication module volume changes at the C3
Maestro effect CEC/IMC CIM line output levels,
not the digital pots within the Enhanced Audio
Enclosure.
Fifteen (15) dual digital potentiometer chips
(integrated circuits) are located on the Audio System Board
for a total of thirty (30) individual pots; there are no
mechanical potentiometers. All audio level adjustments are
accomplished via software. See Table 3. A dispatcher may
adjust the operator's sidetone digital pot using dedicated
keyboard keystrokes <Alt> <Vol
↑
> and <Alt> Vol
↓
> at
the Dispatch Keyboard.
All of the digital pots initially power-up with the wiper
in a 50% or centered position. The microcontroller on the
Audio System Board then immediately loads each pot in
accordance with its respective setting stored in a "working"
area of a serial EEPROM chip on the board. The EEPROM
also contains an unchangeable "default" digital pot storage
area. When shipped from the factory, the working area
matches the default area.
Digital pots may be adjusted using the C3 Maestro
application program via one of its note cards. This function
changes the settings stored in the EEPROM's working area.
Normally, this note card function should only be accessed
by the installation and/or service personnel. To change a
digital pot's setting, the following procedure may be
performed after the console's installation in complete and
it has been powered-up:
1. From the Dispatch Keyboard, simultaneously press
the <Alt> (common control function) and the #
(on numeric keypad) keys. "
Digital Pot Number:
?
" is displayed in the lower left-hand side of the
C3 Maestro's display.
2. From the numeric keypad, enter the number of the
digital pot to be changed. See Table 3. The digital
pot's existing setting is displayed.
3. Press the
↑
(increase) or
↓
(decrease) key to
change the current setting. Changes are saved in
the EEPROM's working area as they are made.
4. Press <Esc> to exit.
SPEAKER ASSEMBLY
Normally, a Speaker Assembly used with the Enhanced
Audio Enclosure is configured at the factory with its
minimum volume feature enabled and its maximum volume
output power set to 2 watts. This configuration is
accomplished by setting two positions on a 4-position DIP
switch located on the Speaker Amp Board.
The following information lists the normal factory
settings and the optional settings which are
available.
Speaker Amp Board
At each Speaker Assembly, a 4-position DIP switch
identified as SW1 is located on the Speaker Amp Board.
One position is used to enable or disable the minimum
volume level feature. A second position allows setting of
the maximum volume level to either 2 or 5 watts of output
power. Factory settings are shown in Figure 3. These
switches have no effect on headset earphone output levels.
Currently, the other two DIP switch positions on SW1 are
not used.
NOTE
SW1 may have a tape seal placed over the switches
to prevent changes.
Minimum Volume Level DIP Switch (SW1 Position 1)
When SW1 position 1 is "
OFF
" or "
OPEN
", the
minimum volume level feature is enabled. This is the
factory setting. With this setting, audio from the speaker
cannot be completely turned off by rotating the volume
control on the Speaker Assembly's front panel fully
counterclockwise.
NOTE
NOTE
NOTE