that it further includes an erasure zone detector 42 which determines whether or not the demodulated complex input signal point falls within an erasure zone and a switch 44 which is positioned to interrupt the connection between phase detector 36 and loop filter 38 in response to an erasure zone detection by detector 42 since the function of phase detector 36 is to generate an error signal proportional to the difference between the demodulated complex input signal z t sometimes referred to as the demodulated baseband signal and the complex data output signal z t and to input such signal to the loop filter 38 for development of a phase reference signal at the input 32 of multiplier 30 the operative effect of erasure zone detector 42 and switch 44 is to prevent the input to filter 38 of those error signals which are considered highly likely to be erroneous more specifically those signals which fall within the erasure zones in fig4 the principal operative components of a preferred embodiment of the erasure zone detector 42 are illustrated and as shown include a complex to real and imaginary converter 50 a toggle switch 52 a zone tester 54 and an or circuit 56 converter 50 is a conventional circuit which separates the demodulated complex input signal z t appearing on line 58 into its real and imaginary components x r and jx i respectively and at a clock rate f s simultaneously outputs these signals on the lines 60 and 62 as indicated toggle switch 52.