https://www.ncbi.nlm.nih.gov/books/NBK21668/ skickar ut signalerna 1-2ms 1-2 ms http://www.ncbi.nlm.nih.gov/books/NBK21668/ 1-2 ms 1-2 ms 1-2 ms https://www.ncbi.nlm.nih.gov/books/NBK21668/ https://www.ncbi.nlm.nih.gov/books/NBK21668/