DLI
16 CHANNEL LOGGER
10
If you’re connecting a radio transceiver, and you’d like to record both the
transmitted and received audio in the same recording file, you’ll need a
4-wire to 2-wire converter. DLI builds custom military intercom and radio
loggers as well as specialized recorders for military and E-911/P25
applications.
Setting the Record Level
Recording levels can be controlled from the front panel using a
membrane keypad: Use the up/down arrows to select a channel, then
use the arrows on the left side to the logger to adjust the recording level.
The slider-bar and speaker help verify audio quality.
It’s important to set the recording level correctly. Low levels are hard to
hear. High levels cause distortion in the recordings, making it difficult or
impossible to decode Caller-ID or DTMF. This distortion is known as
“clipping”. Set each line so the VU meter never quite reaches the red
peak bars during normal recording. If you’re unsure, start by setting the
gain to
0dBm
, turn
Level Boost
off and select
Auto Level
.
To reset all level settings to defaults, press and hold both the up and
down channel selection buttons simultaneously.
Setting VOX Trigger Level and Timeout
To use VOX mode, first adjust the recording level to avoid clipping as
described above. Once the recording level is set correctly, hang up the
line and adjust the VOX trigger level about 6dB above the noise floor.
The VOX trigger level is the threshold at which recording will begin. In
other words, when the logger “hears” a sound louder than the VOX
trigger level, it will start to record. On a line with background noise, you’ll
need a higher trigger level.
Recording will continue until silence is detected for a period of time. This
period of time is called the VOX timeout. Start with a timeout of 30
seconds for phone calls, and 10 seconds for radios. Listen to the
DLI
16 CHANNEL LOGGER
43
D/A Converters
D/A stands for Digital-to-Analog. D/A converters or “DACs” install
between digital lines (usually station sets) and an audio logger. D/A
converters work by converting the signal stream from a digital station set
into the standard analog format used in an audio logger. They are
available in single and multi-channel versions.
Since there is no "standard" for proprietary digital station set
interconnects and line formats, D/A converters are best purchased from
the manufacturer of the PBX. PBX manufacturers often call these
“recording adapters”.
Multi-channel D/A converters are available as stand-alone units or PCI
cards. These cards are sold by Dialogic (now Intel), Algo, and others.
Every proprietary phone switch uses a unique non-standard format, so
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