For nearly 100 years 500kHz has been the maritime calling and distress frequency. It has saved over 10,000 lives, nearly everyone has heard about the Titanic, but in its first decade there are documented instances where over 5000 lives were saved using this frequency.
Much of the credit for the invention of wireless goes to Guglielmo Marconi and this site gives a brief insight into the history of the frequency.
The Radio Officers’ Association is joining other organisations of former marine Radio Officers in calling for 500kHz to be made an International Heritage site.
500kHz, 500kc/s, 600m, 1820ft.
It is all the same !
Over the years the method of expressing measurement of radio frequency has changed or varied from country to country today it is expressed as 500kHz (kilohertz), it used to be termed 500kc/s (kilocycles) and before that 600m (metres) and in some very ancient books it can be found as 1820ft (feet).