train

I am looking to have a period of say 60secs, and within that 60 secs a pulse of 20khz square wave for 20 secs. That pulse of 20 secs can be anywhere within that 60 secs. And then repeated. I am lead to believe 3 x CD4047 can do it ( a bit like using 2 x NE555) but I cannot find anybody doing...