FREQUENCY RESPONSIVE APPARATUS FOR READING A METER OVER A TELEPHONE LINE

摘要

FREQUENCY RESPONSIVE APPARATUS FOR READING A METER OVER A TELEPHONE LINE There is disclosed a system for reading a meter, e.g., a utility meter, over a telephone line. The system includes circuitry for detecting when an input signal within a predetermined frequency range is present. The input signal is fed to two timing devices One of the timing devices is set to produce a constant output when the input frequency is above the higher limit of the predetermined frequency range. The other device is set to produce a constant output when the frequency is above the lower limit of the same range. The outputs of both timing devices are connected to logic circuitry. The two timing devices are connected to the telephone line. When a signal in the selected frequency range is received from the telephone exchange, the frequency detector acknowledges to the exchange the receipt of that signal, and activates a recorder in a meter reading apparatus at the subscriber's location to transmit the recorded reading of the meter over the telephone line to the exchange, where it is suitably recorded. When the first timing device has a periodic output and the second does not, the logic circuitry produces an output indicating that the input signal is within -the predetermined range of frequencies.