A stationary observer/receiver measures the frequency of the light pulses to be f=c/d, where d is the distance between subsequent pulses:

http://www.einstein-online.info/imag...ler_static.gif

An observer/receiver moving with speed v (let v be small so that the relativistic corrections can be ignored) towards the light source measures the frequency of the light pulses to be f'=(c+v)/d:

http://www.einstein-online.info/imag...ector_blue.gif

From the formula f=c/d one infers that the speed of the light pulses relative to the stationary observer/receiver is c. From the formula f'=(c+v)/d one infers that the speed of the light pulses relative to the moving observer/receiver is c'=c+v. Einsteinians disagree:

http://www.wired.com/images_blogs/ph...ixelscared.jpg

Pentcho Valev