This is a sonar technology/operations question.

In the Pacific the Japanese surface ships\' active sonar could switch from the regular mode, with pulses every few seconds, to a high pulse repetition mode, with pulses every second or faster. This mode was used when a ship had a firm sonar contact and was engaging in a depth charge run. The high repetition rate gave better position indication during the crucial final run. The pulses could be clearly heard in the attacked sub by both the sonar, and sometimes by the crew throughout the ship. This was usually a good indication that someone had a good \'lock\' on your position and you were about to get pasted pretty bad.

I haven\'t heard of this in any German accounts of being depth charged, and I am not that up on allied sonar equipment.

-Did the allies (British and US) sonar have a high pulse repetition rate capability?
-Was it used while on a final depth charge run like the Japanese used it?

Thanks in advance....