Auditronics 220 Digital Audio Console, Техническое руководство, Страница: 89 / 109

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220 / March 2000
M E T E R B R I D G E
Digital Timer
The console timer control buttons are located below the timer display.
The timer is provided with an AUTO-RESTART function so pro-
grammed input modules can automatically reset the timer display to zero
and start a new count, allowing the announcer to easily track his own pace.
The START/STOP button halts the timer, holds the last count, and then
restarts and accumulates the count when depressed again
—
perfect for
compiling tapes of desired duration.
RESET has a dual-mode capability:
- if you depress it while the timer is counting, the display will instantly
reset to zero and start a fresh count;
- if the timer is already stopped, depressing this button will reset the
timer to zero, where it will hold until start is pressed.
HOLD button allows you to hold the display for a longer viewing
duration, while still allowing the counter to continue in the background.
Releasing the button will then display the current count.
Console Clock
The Wheatstone digital clock is a six-digit time-of-day clock with LED
display. The clock is designed with CMOS circuits and an on-board
crystal-controlled time base oscillator. There are two basic parts to the
clock: a main PCB containing the clock circuits and clock set controls (also
may include battery or capacitor backup) and second PCB containing
displays. Clock set controls may be accessed by opening the hinged
meterbridge.
Controls
The clock is controlled by a trimmer and two switches; the trimmer and
switches are mounted on the main clock PCB assembly.
The trimmer alters the frequency of the quartz-controlled oscillator,
which in turn causes the clock to run slightly slower or faster. In order to
keep accurate time, the oscillator must run at 4.096 MHz. The oscillator is
set to this frequency at the factory. However, due to the nature of quartz/
crystal-controlled oscillators, there may be a slight change in the fre-
quency of the oscillator during the first few months of operation due to the
aging effect of quartz crystals. A minor readjustment of the trimmer will
compensate for this effect.
A divided by 4 (1.024 MHz) buffered output of the oscillator is available at
pin #7 of IC #U1 to assist in adjusting the oscillator.
220 / Feb 2002