In the latter embrasure, the JM Reibel was mounted on a hinged steel construction that could be swung horizontally out of the way. This system made it possible to make room for an overhead mounted anti-tank gun on a rail. It could be slid forward and locked into position into the embrasure.
One can imagine that changing a weapon during combat was not without risk. When a machine gun mount was swung back, a large gap presented itself temporarily as a welcome target for the enemy. Sometimes during combat, it was simply not possible to change weapons because of the risks involved.
This problem was not present at a few casemates build in, for example, the SF Crusnes after 1935, which were equipped with a weapon-system in an AM cupola that combined a 25mm anti-tank gun and two MAC 31 machine guns.
Interval casemates can be seen as small autonomous forts and were provided with everything necessary to make it self-sustaining for a certain period of time. They provided their own electricity by means of a generator/s (model CLM, 8 hp), had sleeping quarters for the men, filter installations, a radio room, water tanks (for consumption and cooling), rations for a considerable period of time etc. The average garrison consisted of a lieutenant and up to 29 enlisted men.
An armoured searchlight mounted on an armoured pedestal in the rear of each casemate (operated from the inside), illuminated the area's in between them. As one can imagine, using a searchlight was a dangerous undertaking, even if it was armoured. Installation of searchlights on a lot of interval casemates had not been completed just before the outbreak of World War 2.
The intended ammo supply amounted to 600 rounds per anti-tank gun, 40.000 rounds for each JM Reibel, 10.000 rounds for a FM mounted in a cupola and 1000 rounds for close-in defence. Furthermore, there were 240 hand grenades available for the defence of the moats and a 1000 bombs for the 50mm mortar.