{HEAD ~ The output} of the NAND gate is used as {TAIL ~ a first control signal} to set the flip flop and to cause another circuit to activate data transfer 
{ HEAD ~ The output } of the NAND gate is used as { TAIL ~ a first control signal } to set the flip flop and to cause another circuit to activate data transfer
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH