Rx0L Thin Clients

Forgive me since I fair new to newer versions of Wyse Thin Clients. I'm not sure this is the correct thread for this question/issue. I purchased 5 new in open box Rx0L/R10L WTOS 1.5G 128F/512R US CG, P/N 909531-21L, sub-assembly P/N 849233-21L manufactured in Nov 2012. When I boot them up I get a message advising there is no operating system. The older Wyse thin clients I'm currently using boot to a Wyse O/S. I tried find some detailed specs on this unit from the Dell/Wyse web site and could not find any. Do these unit require the use of the WDM software?