def encode(binary_data):
	'''
	Encode binary data using Bell-202 AFSK
	
	Expects a bitarray.bitarray() object of binary data as its argument.
	Returns a generator of sound samples suitable for use with the 
	audiogen module.
	'''
	framed_data = frame(binary_data)

	# set volume to 1/2, preceed packet with 1/20 s silence to allow for startup glitches
	for sample in itertools.chain(
		audiogen.silence(1.05), 
		multiply(modulate(framed_data), constant(0.5)), 
		audiogen.silence(1.05), 
	):
		yield sample