Sensitivity Analysis of the 47A Signal
R. Longhitano · Bell System Technical Journal · 1980
The 47A Signal is the physical component of 1D-type electronic coin telephones which detects coin deposits and consequently initiates the transmission of coin-deposit information to the central office. Manufacturing problems encountered in initial production units of the Signal prompted Bell Laboratories to investigate the Signal design and operation. Rather than resort to a series of time-consuming empirical experiments to quantify the interaction of various Signal design parameters and their influence on Signal performance, we formulated a finite element model of the Signal's coin sensor. Consequently, these experiments could be performed via computer. This computer-based sensitivity analysis led to the conclusion that the coin sensor design was highly susceptible to manufacturing variables. By changing the dimensions of one of the coin sensor components, a piezoelectric ceramic, this susceptibility was eliminated. The computer-based experiment was, therefore, demonstrated to yield rapid, easily interpretable results. Moreover, resource usage was minimized when compared to a conventional laboratory approach. The results of the computer-based experiment were confirmed by production data.