Sonobuoys
There are two basic types of sonobuoy; passive and active, both are dropped into the sea by aircraft to locate enemy submarines. Both are expendable devices and on completion of their mission are scuttled.
A passive buoy sits on the surface and deploys underwater hydrophones, which pick-up underwater "noise". The "noise" is transmitted to "receivers" on-board surveillance aircraft to enable operators to identify enemy targets and their approximate direction. The battery is used to power the transmitter.
An active buoy has the ability to identify targets at much longer range by "pinging" them with a high power acoustic signal and picking up reflected noise with its hydrophones. By using a group of buoys the operator can pick up both direction and range. Generally an active buoy will have two batteries, one for the power amplifier to send out the acoustic signal and one for the transmitter.
In both cases the batteries used are primaries. The typical battery specifications are as follows:
| Passive | Active | |
|---|---|---|
| Capacity | 3.75 Ah | 5.0 Ah |
| Voltage Range | 11V - 18V | 30V - 48V |
| Charging | NA | NA |
| Operating Temperature Range | -2°C to +35°C | -2°C to +35°C |
| Maximum Discharge Current | 3.5A | 36A |
| Form Factor | 6series | 16series |
| Communications | None | None |
