5 rem Generates a telephone sound continuously
  10 dim y
  20 dim x, z
  30 dim speaker as pin pt2 for digital output
  40 let y = 100
  50 let z = 1
  60 while 1 do
  70   for x = z to y
  80     let speaker = !speaker
  90     sleep x us
 100   next
 110   for x = y to z step -1
 120     let speaker = !speaker
 130     sleep x us
 140   next
 150 endwhile