Glossary

Automatic Gain Control (AGC ): Automatic Gain Control changes the gain level as the receiver deems necessary without input from the user.

Background noise : Background noise is the total noise from all sources other than the sound of interest.

Blanking Interval: The Blanking Interval is the length of time (in milliseconds) after an acoustic signal has been received in which the VEMCO receiver will ignore any subsequent signals. This is to eliminate the reception of echoes by the receiver.

Channel: A channel in VEMCO receivers 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.

Coded Map: A coded map is a group of four submaps operating on the same frequency. There are four standard coded maps for use with VEMCO’s coded tags.

Coded Submap: A submap is a portion of a coded map to which a coded tag type is assigned, either R256, R04K, R64K, or S256.

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 fix or random delay. The type and length of the delay is set at the time the tag is ordered and can’t be changed once the tag is built. The types of coded tags available are listed in the table below with the number of ID numbers available, the number of pings in the ping train, and if a sensor is available.

Continuous tags: Continuous tags transmit the acoustic pings continuously, without long 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.

Decibel (dB): A decibel is a unit used for measuring the strength of a signal. A decibel is one tenth of a "bel".

Map: see Coded Map.

Pinger: A pinger is a VEMCO tag that contains no sensors. It can have either a coded or continuous transmission schedule.

Position dilution of precision (PDOP): PDOP is a unitless measure that indicates when satellite geometry will provide the most accurate results. A low PDOP indicates the satellites are nicely arranged to give a good position. The PDOP may be improved by facing the GPS antenna towards the equator where more satellites are located.

Tag: A VEMCO tag is an acoustic transmitter that is attached to a marine creature and transmits an acoustic signal. The acoustic signal is received by a VEMCO receiver. VEMCO tags can transmit either a coded or continuous signal, with or without sensor data. After a tag is powered, it will continue to broadcast according to factory setup until powered down.

Sensor transmitter: A sensor transmitter is a VEMCO tag that has at least one sensor. The type of sensor is usually included in the transmitter’s name. For example, a V16P has a pressure (depth) sensor and the V16T has a temperature sensor. A sensor transmitter can also have either a coded or continuous transmission schedule.

Submap: see Coded Submap.