Metering pulse
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In telecommunications signalling, metering pulses are signals sent by telephone exchanges to metering boxes and payphones aimed at informing the latter of the cost of ongoing telephone calls.
The properties of these signals differ between countries, but they typically have a frequency of 50Hz, 12kHz or 16kHz, and a duration of several tens or hundreds of milliseconds.
Each pulse represents a certain incremental cost. Therefore, during more expensive calls the exchange will generate more metering pulses per minute than during cheaper calls.
See also: Automatic Message Accounting
