Range control system

Claim 1

An indicator comprising: a base; a first member having first and second sets of letters thereon, said first set including the letters B, R, O, I and L, said second set including the letters B, A, K and E, said letters B, A, K and E being positioned on said first member contiguous to the said letters B, R, O and I, respectively; a second member having a construction to mask all of the letters in both of said sets, but not all at one time, said second member having a construction so as to mask all of the letters of said first set without masking any of the letters of said second set and vice versa, said second member being opaque except for certain aperture means therethrough, said aperture means always masking at least five alternate ones of the letter spaces; mechanical means to move one of said members back and forth between two positions relative to said base and in directions along a line, all of said letters being aligned in succession along said line; and means to mount said one of said members movably relative to said base, the other of said members being fixed relative to said base, said aperture means including five spaced apertures located on approximately the same said line, each aperture having a width equal to the width one letter space and being at least as large as one letter in height, each said apertuRe being spaced from each aperture adjacent thereto a distance approximately equal to one letter space width, said two positions being spaced apart one letter space, said letters being arranged in a series in the order B, B, A, R, K, O, E, I and L, no substantial space being provided between the letters except the letters I and L, one blank letter space being provided between the letters I and L.