     init_mode("Pulse Mode");
     
     while (system_mode == 0) {
+      act_on_estop()
       read_controls();
       update_bottom_display_line();      
 

    init_mode("Pink Noise");
    int delay_time;
    while (system_mode == 4) {
      read_controls();
      update_bottom_display_line();



    digitalWriteFast(channel_1_out, LOW);
    digitalWriteFast(channel_2_out, LOW);
    vfd.setCursor(0, 0);
    vfd.print("      ESTOP     ");
    // Require HW reboot to exit
    while(true) {};

  }
}

