13. (1) Every diagnostic x-ray machine that is equipped with an automatic exposure control shall be equipped with, (a) an indicator that shows when the automatic exposure control mode of operation has been selected; (b) a means of terminating the exposure, (i) of an x-ray tube with a potential of less than fifty kilovolts peak, when the product of the x-ray tube current and the exposure time is 2,000 milliampere-seconds per exposure, or (ii) of an x-ray tube with a potential of fifty kilovolts peak or more, when, (A) the product of the x-ray tube current and the exposure time is 600 milliampere-seconds, or (B) the product of the peak x-ray tube potential, current and exposure time is sixty kilowatt-seconds per exposure; and (c) an indicator that warns the operator that a condition set out in subclause (b) (i) or (ii) has been reached. (2) Every diagnostic x-ray machine shall be so constructed that, (a) over the normal range of use of the machine for any given combination of x-ray tube potential (in kilovolts peak), tube current (in milliamperes), exposure time (in seconds) or for selected radiation exposure to the image receptor (in milliroentgens), (i) the estimated coefficient of variation of any ten consecutive radiation exposure measurements taken at the same source-to-detector distance within a time period of one hour is no greater than 0.08, and (ii) each of the ten radiation exposures referred to in subclause (i) is within 20 per cent of the mean value of the ten measurements; (b) for any selected setting of the peak x-ray tube potential over the normal range of use of the machine, the average peak kilovoltage corresponds to the selected value to within + 8 per cent; (c) the timer on the x-ray machine may be set to control irradiations as short as 1/30 second or five milliampere-seconds, whichever is greater; (d) at each setting over the normal range of use, the timer on the x-ray machine is accurate to within + 10 per cent; and (e) at each setting over the normal range of use, the timer on the x-ray machine will comply with the reproducibility standards set out in clause (a). (3) Subsection (2) does not apply to dental x-ray machines, chiropodic x-ray machines or to mammographic x-ray machines. (4) Where a diagnostic x-ray machine is constructed so that the tube current (in milliamperes) has a range of preset values and both it and the exposure time (in seconds) can be selected individually, the average ratios of exposure (in milliroentgens) to the product of tube current and exposure time, obtained at any two adjacent tube current settings for any fixed indicated value of x-ray tube potential (in kilovolts) over the normal range of use of the machine, shall not differ by more than 0.10 times their sum or  where x1 and x2
are the average mR/mAs (milliroentgens divided by milliampere-seconds) values obtained at the two selected settings of mA (milliamperes). (5) Where a diagnostic x-ray machine is constructed so that the exposure selection can be made only as the tube current exposure time product (in milliampere-seconds) or where the milliampere value is continuously variable, the average ratios of exposure (in milliroentgens) to the product of tube current and exposure time, obtained at any two selections of milliampere-second differing by at least a factor of two, for any fixed indicated value of x-ray tube potential (in kilovolts) within the range of normal operation of the machine, shall not differ by more than 0.10 times their sum, or  where x1 and x2
are the average mR/mAs (milliroentgens divided by milliampere-seconds) values obtained at the two selected settings of mA (milliamperes).  R.R.O. 1990, Reg. 543, s. 13.