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