Unit installation

6-19
RLC-3 V1.80 Copyright © 1998 Link Communications Inc. 9/17/98
size or number of simms installed, or the simms may be faulty. If there are only a few errors, you
may be able to use the simms with errors in the RAM #2 sockets with only a slight loss of audio
quality. Errors in the simms installed in the RAM #1 sockets are likely to cause serious problems.
The memory test performed when the DVR is powered up is very thorough and therefore can take
quite a while, especially if you have a lot of memory installed, so you may have to wait for it to
finish before testing. With 2, 4, 8 and 16 megabytes of memory, the test takes about 20, 40, 80 and
160 seconds (about 2.5 minutes), respectively. Since you won't be powering up very often, this
shouldn't be a problem.
If you have the serial port connected and the serial screen scrolls constantly after the memory test is
finished, it is probably because you don't have the DVR connected to the controller, or the
controller is not powered up.
Audio Quality/Recording Time:
The audio quality of tracks played with the DVR is nearly identical to the original. You will
probably not be able to distinguish between a recording and someone talking "live." Technically,
the DVR samples and plays audio at 8KHz with 8 bit resolution (256 voltage levels). This uses
64000 bits per second, which is 8000 bytes per second. At this rate, each megabyte of memory will
hold 131 seconds of recorded audio. A small portion of the memory is used for other purposes, so
the actual amount of storage will be slightly less than 131 seconds per megabyte. In a future
software version, it may be possible to record with lower quality to extend the recording time.
Adjusting the DVR:
There are only two adjustments on the DVR: record level and playback level. Both are preset
before the DVRs are shipped, and should not need to be changed, at least for initial testing.
When/if you do decide to adjust the levels, the playback level should be set so that the audio is
played back at the same volume it was when it was "live". If you decide to change the record level,
the playback level should be adjusted again before any judgement is made as to whether the new
record level is better or worse. The record level is important because it affects the quality of the
recording. If it is set too low, the full resolution of the digital storage will not be utilized and there
will be more background noise in the audio than is necessary. If the record level is set too high, the
audio peaks will be clipped off and the audio will sound distorted, especially the loudest parts.
There are many factors that determine the best level, so experiment with the Audio Check
Command and adjust the record level until it sounds the best. Looking at the audio with a scope as
it is played back will help identify if the record level is set too loud, as the top and bottom of the
waves will be flattened (a little bit of clipping on the louder parts is normal and expected). If you
have a computer or serial terminal hooked up, you can also record a message with Command 171
and look at it with the software oscilloscope function to see how much of the available range you
using.
The record and playback levels can be returned to the factory settings as follows: Set up a service
monitor to generate a 1KHz tone with 3KHz deviation. Adjust the controller to get one volt peak
to peak at the audio test point on the controller (the way the controller receive level is normally set