 A prototype of the automatic strobe unit was produced in October , along with a new Mk . IVA @-@ like radar unit with a manual strobe for testing . EMI was then asked to provide another breadboard prototype of the strobe unit for air testing , which was delivered on 12 October . A raft of problems were found and addressed . Among these , it was found that the strobe would often stick to the ground reflection , and when it did not , would not stick until it had a strong signal at shorter ranges , or might stick to the wrong target . Eventually a panacea button was added to <unk> the strobe in these cases . 
