The ripple blanking doesn't have to be simple, either. Depending upon how you deal with the pins and overall circuit configuration, you can have leading-zero blanking, trailing-zero blanking or both. You can force the blanking of any or all digits, so if you have a display where you'd like to indicate an overrange condition, you can force-blank the entire display at a 0.5-second rate using a 555 timer gated into the RBO/BI pins. Or, you can use these same pins with the same gating and the same (or another) timer to change the blanking pulse width at a 100Hz frequency to provide efficient display brightness. If you're really good (and I've been known to be on occasion), you can use a single 7447 with a multiplexed display and still have leading-zero blanking using a single flip-flop to store the RBO data for the next switch of the MUX.
Dean