Dr. Harrison Wells agreed to help Hunter Zolomon steal the Flash's speed due to the latter's threat on his daughter's safety. A concrete plan started to form when Team Flash captured Russell Glosson; Wells later took a further step by getting a brain tissue sample of him in order to study him, consequently killing Glosson in the process. Wells recorded his journal entry 1-14 on his next gen watch that, by studying the Turtle's brain matter and the encounter with the Reverse-Flash, he completed a device that could harness the Flash's speed when he tapped into the Speed Force, which he installed behind the Flash's white emblem of the Flash suits. It proved to have worked when the Flash went to face Joseph Monteleone for the first time; Wells successfully transmitted some of the speed and later on gave it to Hunter Zolomon.
Later, this device was made to transfer the energy of the tachyon device to Barry's emblem for convenience and to conceal it against Hunter in order to improve his speed without having to put the device on. After Hunter captured Wally however, this device was once more used to steal all of The Flash's speed in turn releasing Wally, turning Barry Allen into a normal human and curing Hunter.
In order to take Barry back from the Speed Force once he rescued Wally West, Cisco inserted "goldtooth" technology into it. However, when Barry was given a test to battle the now enslaved Hunter Zolomon, Barry used the transmitter to destroy Zolomon for a temporary amount of time.
Another version of the transmitter was used on Barry when Team Flash attempted to take Nora back into her time by recreating what Barry did with Supergirl in order to return to his Earth. However, due to the negative tachyons Nora kept in order to prevent traveling back, this attempt failed.
Years after the device was used to steal Barry's speed, Team Flash created an idea to develop a weapon to stop a new villain, "Cicada". In order to build it, Barry and Nora traveled back in time in order to retrieve the necessary pieces for it to work, the transmitter included. Unfortunately, in a battle with Zoom, the transmitter was damaged and Barry and Nora had to seek help from Eobard Thawne in 2015 to fix it before building the device.