switch (prm.type) {
  case 0: prm.tf = 0; prm.ts = 0; break;
  case 2: break;
  case 3: prm.ts = prm.ti-prm.tf; break;  //ignor!!!
  case 4: prm.tf = prm.ti; prm.ts = 0; break;
  default: prm.ts = 0;
  }