{HEAD ~ DS3 byte counter} counts {TAIL ~ the DS3 AIS/Idle code bytes} and generating an AIS/Idle bytecount enable control signal if the number of DS3 AIS/Idle code bytes is less than a predetermined number of DS3 bytes to be mapped in a given row of the STS 1 frame 
counts
{ HEAD ~ DS3 byte counter } counts { TAIL ~ the DS3 AIS / Idle code bytes } and generating an AIS / Idle bytecount enable control signal if the number of DS3 AIS / Idle code bytes is less than a predetermined number of DS3 bytes to be mapped in a given row of the STS 1 frame
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH