Call Indicator for Telephone (May, 1931)
Call Indicator for Telephone
THE numbers dialed on automatic telephones can now be recorded on a call indicator device invented by William Green-berg of Portland, Ore. In the center of the regular telephone dial is a space where the numbers being dialed are reproduced, showing what number is being called, and warning immediately of any error. Pressing a small button at the top of the device clears the figures for the next call.