{HEAD ~ The current flow} produces a potential difference across the first diode to turn on {TAIL ~ another transistor} to cause an alarm to be given 
{ HEAD ~ The current flow } produces a potential difference across the first diode to turn on { TAIL ~ another transistor } to cause an alarm to be given
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH