{HEAD ~ DS3 AIS/Idle code generation} means generates {TAIL ~ DS3 AIS/Idle code bytes} in response to the local STS 1 clock signal 
{ HEAD ~ DS3 AIS / Idle code generation } means generates { TAIL ~ DS3 AIS / Idle code bytes } in response to the local STS 1 clock signal
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH