You might have 2 mistakes in code: path and extention. And use the following formats as well as ttf:
@font-face {
font-family: 'const';
src: url('const.eot'); /* IE9 Compat Modes */
src: url('const.eot?#iefix') format('embedded-opentype'), /* IE6-IE8 */
url('const.woff') format('woff'), /* Modern Browsers */
url('const.ttf') format('truetype'), /* Safari, Android, iOS */
url('const.svg#svgFontName') format('svg'); /* Legacy iOS */
}
urls that helps to create web fonts: