Sensor location Most starting gates are located in the center of the lane. Therefore, the finish gate sensor should be located in the center of the lane also. For example, if the finish gate sensor is located at the wheel, cars with long noses will have an unfair disadvantage because their front wheels start behind the front wheels of other cars. I've heard that visible-light optical sensors are subject to spoofing by flash photography, and that infrared optical sensors are immune to this effect. An electronic finish gate should be accurate to within a millisecond or less, otherwise you might have results that are obviously incorrect.
More accuracy is even better.
The following companies sell electronic finish gates. I am not affiliated with any of them, and unless noted, I have no experience with their products or service. My CSB Stockade unit bought our finish gate from Summit Finish Lines. It uses infrared sensors, and displays first, second, and third place. With the stand-alone display, everyone in the room can see who finished in what place.