input 86 of divider 35 divider 35 therefore provides at its output 87 a third analog signal which is proportional to the quotient of the first total count and second total count the first total counts form the numerator of the quotient and the second total counts form the denominator of the quotient the third signal at output 87 of divider 35 represents call queue seconds divided by the calls handled as averaged over the past 100 seconds this signal will change or be updated each ten seconds the result of this division is the average wait time for service in seconds that each call subscriber has experienced during the last 100 second period output 87 of divider 35 is coupled to input 88 of log amplifier 36 so that log amplifier 36 provides at output 89 a fourth signal having a magnitude proportional to the log of the magnitude of the third signal the fourth signal is transfered to the pen recorder 37 wherein the pen recorder displays the resulting average wait time on a running chart where the result is traced on log paper having a three decade range 0 1 to 100 seconds because the object is to maintain the average wait time at approximately two seconds and because two seconds appear on the log paper substantially in the center of the log paper diviations from center or the desired wait time may be readily detected also because the average wait time is being recorded on a running chart recorder the average wait times are in such a condition as to provide an historical record of system performance while a particular.