Space was reserved for an unsuccessful French sonar system that was cancelled in September 1930. The NGS also intended to fit a passive Walser acoustic locator system in the "Chacal" class, but only was actually fitted with one. This consisted of a set of two steel lenses, one set on each side of the ship, with a large number of diaphragms that ambient amplified sound for the operator. This proved useless while the ship was moving faster than dead slow and was removed in 1931. The Walser compartment was reused when a British Type 123 ASDIC system was installed aboard the ships in 1939–40, although "Panthère" did not receive one.