HO Steam Locomotive Whistle Sound Push Button....!!! With a touch of your finger on the button, you will hear the authentic sound of a Steam Locomotive passing by blowing it's whistle at every crossing. If desired, the button is recordable for your own selected train sound. Allowable recording time is 30 seconds. 2 AAA batteries required, not included. Postage cost: $5.00 The blue button measures: Diameter, 3.5 inches. Height, 1.5 inches. This sound button is a MUST addition to any HO layout and stock equipment that are not DCC. ALL ABOARD! Ask to send a video of how it sounds. Just super!!