'DORJI DRF DRF7020D13 433 MHz transceiver trial setup  July 2011 
'makes use of the slight reading "wait" of PULSIN
dorji:
serout 2,n1200,(b0)      ' b0 just a handy "placeholder"- can be anything
pulsin 4,0,b1            ' reads & briefly awaits any reply
if b1=0 then dorji       ' if nothing heard then "ping" again & await reply

serin 4,n1200,b0         ' routine when a response heard after pinging
pulsout 1,200            ' LED flash indicating data received
goto dorji