  A graphical presentation of the timing of avalanche photodiode events in the
datasets from the experiment of Weihs et al. [Phys. Rev. Lett. 81, 5039 (1998)]
makes manifest the existence of two types of signal delay: (1) The introduction
of rapid switching of the input to a pair of transverse electro-optical
modulators causes a delay of approximately 20 nanoseconds for a proportion of
coincident avalanche photodiode events; this effect has been previously noted,
but a different cause is suggested by the data as considered here. (2) There
are delays that depend on in which avalanche photodiode an event occurs; this
effect has also been previously noted even though it is only strongly apparent
when the relative time difference between avalanche photodiode events is near
the stated 0.5 nanosecond accuracy of the timestamps (but it is identifiable
because of 75 picosecond resolution). The cause of the second effect is a
difference between signal delays for the four avalanche photodiodes, for which
correction can be made by straightforward local adjustments (with almost no
effect on the degree of violation of Bell-CHSH inequalities).
