Arrangement for registering and reading of message units in telephone exchanges

An arrangement for registering and reading message units for calls in a telephone or Telex exchange to allow automatic billing for calls and presenting the bills to the subscribers of the exchanges. Electrochemical integrators are connected so that one of their electrodes is connected to ground potential, whereas the other electrodes of these integrators are connected over resistors to wires conducting metering pulses to individual equipments of exchange lines. The latter electrodes during the reading process become connected over a commutator to a reading device having threshold means detecting the increase of voltage on terminals of the integrator. A generator provides square pulses having their polarization opposite to that of the metering pulses. The output of the generator is connected to a gate having its other input connected to the threshold means. The output of the gate is connected to the input of the pulse counter. The output of the pulse counter and the output of the commutator are connected with a device for registering the read pulses and commutator position.