The HOW FAST Airspeed Instrument provides you with a simple, easy, and in expensive way to measure your model's air-speed. It provides at-the-field readings right after your flight-without the need for a computer or any additional equipment. The Airspeed Indicator measures airspeed using the same technique that is used in full-scale aircraft-differential pressure sensing. The included pitot and static probes normally mount in the leading edge of your plane's wing. In some applications (gliders, pushers, twins, and jets, the probes can be mounted in the nose of the aircraft. The same alignment and spacing guidelines apply. Just plug the connector into any unused servo channel on your receiver. If all channels are in use, you can use a "Y" adapter and share a channel with a servo. If you need longer wires just use a longer servo extension. The indicator samples the airspeed every second throughout your flight. After the flight, activate the airspeed report before turning off power. With the LED pointing toward the sun, or the brightest part of the sky, wave your finger back and forth across the LED. When the unit recognizes your wave, the LED will come on for 4 seconds. At this point, stop waving and start counting! It will report the maximum airspeed by flashing the LED. For example: a peak speed of 123MPH will report as one flash followed by a pause, two flashes, another pause and then three flashes.( flash flash-flash flash-flash-flash). Each group represents one decimal digit. Leading zeros are suppressed, so 89 will report as 8 flashes, pause, 9 flashes. A zero is represented with by a quick double-flash. After the last flash of the speed report the LED will be dark for about 4 seconds then resume it's 2 second heartbeat. Standard units report in miles per hour. Once you have activated the airspeed report, the results are stored away in memory. You can then turn power off. You can repeat the airspeed report as often as you like ( in case you miscounted or forgot the result). When your next flight exceeds a speed of about 15MPH, the system will recognize the new flight and allow the old data to be replaced.