An optical touch system including a touch surface, a plurality of image sensors, a calculation unit and an identification unit is provided. The therapeutic or prophylactic agent comprises as an effective ingredient a glycine derivative having a specific structure or a pharmaceutically acceptable salt thereof, for example, the below-described compound -2–5-4-phenylpent-4-enoic acid. The trailer signal converter selectively drives the turn and stop light signals on the trailer based on the input signals. The value of the signal quality metric is compared to a threshold and based on this comparison various decisions are made by the medical device. The aqueous solution of an ethylenimine polymer can be purified by heating and condensing it. A hammer element may be integrally formed with the substantially conical frustum and extend there from in one radial direction.