RTL Dynamic Microphone Type 630 Hi-Z The Radio Technic Labratory. The RTL Dynamic Microphone are variant of the 1940's Electro Voice 1st generation 630 microphone. This particular model was sold under license by E.V and sold under the R.T.L brand name. They called it the type 630 which was identical in every way to the E.V model of that time. Electro Voice sold a few of it's mics to other companies such as Pierce, Rauland Borg, Auricon and Dukane to name a few. This mic comes with the period astatic stand in which to display. It measures 5" Diameter x 11" H.