Max operating voltage often is specified in an unprofessional way, also for rc components such as receivers and servo's.
For instance,
"Power requirements :4.8V or 4 nimh or"
"6V or 5 nimh or 4 alkaline's"

5 nimh fully loaded can be well over 7V and 4 alkaline's is 6.6 V, so this type of specification is confusing.
Better would be
"Power requirements :4 to 5 nimh or"
"4 alkaline's "
"absolute max continous operating voltage 7.2V"
"minimum operating voltage 3.8V"