 However, much of this evidence is based on reports from a neighbor who made these claims after 1876, when knowledge of the transmitter had already been stolen from Gray.For some examples of these transmitters, see Figures 3, 4a, 4b, and 5 above, as well as the drawings for Bell's 1875 patent, 6a and 6b.After March 1876, Bell focused on improving the electromagnetic telephone and never used Gray's liquid transmitter in public demonstrations or commercial use.