Chip Timing is a technology for sensing and recording the finishing times of all runners in a race. It's much more accurate and can easily deal with the old problem of many runners finishing nearly at once in a big, crowded race. The "chip" is a tiny electronic chip that's programmed with a runner's specific runner identification. A runner attaches the chip to his shoelaces. It sends a signal to an electronic reading device—often hidden under a strip of carpet—when a runner crosses the start line and again when he crosses the finish line. No human observation is necessary. The runner's exact time is recorded automatically.
Chip timing is a nice service to offer your runners because it gives them the exact time of their run. However, gun time is always considered the official time, even in races that use the chip. The reason for this is that you want the first person who crosses the finish line to be the winner, not someone who started later and crossed the finished line afterwards. Though you will be presenting awards based only on gun time, publish both results, since runners are likely to want to see both times.
If you use chip timing, you will need to rent materials (chips and electronic reading devices) through a timing company. Keep a separate area away from registration or packet pick up for runners to pick up their chip on race day. When you set up the electronic reading devices, be sure to enclose them so that runners run over them and can not run around them (and therefore not record a time). It also may help to set up a reading device in the middle of the run, to discourage runners from cutting the course and cheating.
At the end of the race, have your volunteers stop runners before they leave the finish area to collect the chip timers from their shoes. The times and runner info are stored on the chip, and the timing company will be able to retrieve it. Be sure to collect all timing chips to avoid penalty fees by the timing company.