pulse2.css

.ring {
    width: 300px;
    height: 300px;
    border-radius: 50%;
    position: absolute;
    background-color: transparent;
    border: 15px gray solid;
    -webkit-animation-name: ani; 
    -webkit-animation-iteration-count: infinite;
    -webkit-animation-timing-function: ease;
    -webkit-animation-duration: 6s;
    -webkit-animation-direction: reverse;
   
}

@-webkit-keyframes ani {
    0% {-webkit-transform: scale(1); opacity: 0;}
    10% {-webkit-transform: scale(1); opacity: 1;}
    99.9% {-webkit-transform: scale(0.1); opacity: 1} 
    100% {-webkit-transform: scale(0.1); opacity: 0} 
}

#r2 { -webkit-animation-delay: 1s;}
#r3 { -webkit-animation-delay: 2s;}
#r4 { -webkit-animation-delay: 3s;}
#r5 { -webkit-animation-delay: 4s;}
#r6 { -webkit-animation-delay: 5s;}