Complex sentence: The trawler was armed with one inoperable 3-inch naval gun, two machine guns and four depth especially charges but lacked sound and degaussing equipment which meant that she had to be careful around the mines and could only attack a submarine if one was spotted visually.
Split into simpler sentences: The trawler was armed with one inoperable 3-inch gun, two machine guns and four depth charges but lacked degaussing euipment and sonar. This meant she had to be careful around the mines and could only attack a submarine if one was spotted visually.