The first horse-drawn tramlines did not use any special labeling as they were radially inferior from the respective endpoints in the center and thus had few points of contact with other lines. Only with the expansion of the network into the city center was there a need to distinguish the lines from each other. From the 1880s, most major German cities therefore used colored target signs or signal boards, sometimes both together. In Berlin, these were always kept in the same combination. As identification colors red, yellow, green and white were used, from 1898 additionally blue. The panels were one or two colors, the latter either half / half divided or in thirds with a line in the second color. However, the number of signal panels used was not sufficient to equip each line with its own color code. In addition, crossing or side by side lines should run with different signal panels. This meant that individual lines had to change their color code several times in the course of their existence. As a result of the electrification and the takeover of the New Berlin Horse Ride by the Great Berlin Horse Railways / Great Berlin Tram (GBPfE / GBS) increased their number of lines at the turn of the century abruptly. With a view of the Hamburg tram, where in the summer of 1900 for the first time in German-speaking countries line numbers were introduced, experimented the GBS from 1901 also with the numbers. In the timetables of this time, the lines were numbered, but could change their order every year. The numbering scheme should include not only the GBS but also its secondary lines. At the same time, letter-number combinations as they appeared in the timetable booklet should be avoided.