VEMCO – VR100 Receiver Operating Manual – Page 50
5.3 GLOSSARY
Automatic Gain Control (AGC):
Automatic Gain Control changes the gain level as the VR100
deems necessary without input from the user. The VR100 uses signal strength to determine if the
gain level should increase, decrease, or remain constant. In most conditions, the VR100 should be
used in the manual gain mode. Section 4.2 explains how to switch between manual and automatic
gain control.
Blanking Interval:
The Blanking Interval is the length of time (in milliseconds) after an acoustic signal
has been received on a given channel in which the VR100 will ignore any subsequent signals on
that same channel. This is to eliminate the reception of echoes by the receiver.
Background noise:
Background noise is the total noise from all sources other than the sound of interest.
Channel:
A channel in the VR100 is a group of configuration settings used to listen to VEMCO tags.
For example, a channel can be configured to listen for continuous pingers that operate at 60 kHz.
Another channel can be configured to listen for coded tags operating at 69 kHz. Up to eight
channels can be monitored simultaneously.
Code Map:
A Code Map describes a collection of Code Spaces. When a receiver is configured with a
particular Code Map, it can detect and decode all the types of transmitters in that map. See Table
4.3-3 for a list of supported maps. MAP-113 is the current default map for 69kHz transmitters and
allows the VR100 to properly detect and decode all currently supported VEMCO Tags.
Code Space:
Code Space describes all the parameters that a receiver needs to properly decode each tag.
These parameters include the numbers of pulses, the coding technique, the length of the first
interval etc. Tag specification sheets will always include a Code Space value. Users must ensure
that they select a code map that contains the code space(s) of the tags they are detecting.
A69-1303 is an example of a valid Code Space label. The “A69” indicates an Acoustic Tag
operating at a frequency of 69 kHz. The “1303” is a unique number that is understood by the
receiver firmware to determine how to detect and decode the tags. The VR100 Receiver will report
tag detections as Code space and ID#. It is important to note that a tag that transmits a Code space-
ID#, e.g., A69-1303-2056, is a different transmitter then one with a label of A69-1206-2056. The
ID codes are the same but the Code Space is different and uniquely identified by the VR100!
Coded tags:
Coded tags transmit a series of acoustic pings to form an ID (identity) number recognized
by the receiver. The pings form a “ping train” that is usually followed by either a fixed or random
delay. The type and length of the delay is set at the time the tag is ordered and cannot be changed
once the tag is built.
Continuous tags:
Continuous tags transmit the acoustic pings continuously, without delays between
transmissions. Continuous tags are available with or without sensors.
Coordinated Universal Time (UTC):
UTC is the international time standard. It is the current term for
what was commonly referred to as Greenwich Mean Time (GMT). Zero (0) hours UTC is
midnight in Greenwich, England, which lies on the zero longitudinal meridian. Samples of the
conversion factor needed to convert from UTC to the local time zone are found in Table 4.3-1.
