Siren signals are the particular language of ships by means of which the steersman communicates with the shore or other vessels to ensure safe operation or for other purposes.

The siren produces sounds of long and short length, the long ones lasting 4-6 seconds and the short ones about one second. The combination and sequence of long and short notes convey different meanings. Perhaps it is interesting to interpret some of the twenty siren codes currently used by Chinese ships on inland navigation lines:

3⁄4              I am shoving off

3⁄4 3⁄4          Permit me to moor or pass through lock

3⁄4 ·            I am turning starboard

3⁄4 · ·        I am turning port

3⁄4 3⁄4 ·      Permit me to overtake on your port

3⁄4 3⁄4 · ·      Permit me to overtake on your starboard

3⁄4 · · 3⁄4     Wait until I have passed

3⁄4 · 3⁄4 ·   Your request accepted

· · · ·         Your request cannot be accepted

· · ·             I am going astern

3⁄4 3⁄4 3⁄4      Passenger overboard

· · · 3⁄4       I need help