Canon MACRO RING LITE MR-14EX II Mode D'emploi page 72

Flash Firing Restriction due to Temperature Increase
Even when Level 1 warning is not displayed, the firing interval will be
extended as the flash unit begins to heat up.
If Level 2 warning is displayed, allow a rest time for at least 15 min.
For cautions on the number of flash firings, see page 12 (continuous
flashes) or page 23 (modeling flash).
Do not touch the flash unit or batteries immediately after firing continuous
flashes or modeling flash. Touching them may result in a burn. Before
detaching the flash unit or replacing batteries, make sure that the flash
unit has cooled.
When C.Fn-22-1 is set (p.64), the warning with red illumination of LCD
panel will not be displayed even if the temperature of the flash unit rises.
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