M201 - siren / sirčne
24 volt french sirens certainly exist but in the main they were fitted to heavy armoured vehicles. To say that they were never fitted to the M201 would be not quite true, though it was a rare occurrence. The photo above (from 'Only in a Jeep' by Jean Gabriel JEUDI) shows an M201 of the 5th armoured regiment complete with siren. The word 'DEPANNAGE' (REPAIRS) displayed under the windscreen indicates a fast response light repair team hence also the amber beacon. If their attempts at a roadside repair failed then the job would have to be left for a heavy recovery team.
The somewhat battered example of a French siren shown above has in fact never been used on a vehicle. It is similar in design to some American sirens that I have seen but there is no manufacturers data plate to give a clue as to its origin. The instructions indicate that the siren requires lubrication on installation and monthly thereafter to keep it in good working order.