Simrad SP90 Operator's Manual page 3

Simrad SP90
Low frequency long range fishery sonar
Software version V1.1.XX
The sonar must never be powered up when the ship is
in dry dock. The transducer will be damaged if it
transmits in open air. To prevent inadvertent use of the
sonar, set switch S102 at the rear side of the Sonar
processor Unit to Off whenever the vessel is in dry dock.
WARNING
850- -164511