| 摘要 |
Impulse metering at local telephone switching offices in a DAMA DOMSAT communication system involves the storage of billing rate information in the control computer equipment at a master station. This billing information is maintained in the form of a look-up table containing all billing rates to apply to toll calls. Since the control computer knows the identity of the calling and called offices, it can select the proper billing rate for the call. Respective relatively remotely located interface stations, to which local exchanges are connected for coupling a subscriber with the satellite link, contain signalling converter circuits which, in addition to interpreting the dialed telephone number and formatting digital signals containing the dialed information, forward digital signals to a DAMA system controller where the signals are formatted and combined with other signals being transmitted to the master station. The signal converter includes billing pulse metering circuitry which responds to billing rate information transmitted by the master station when the calling party answers the call. This billing rate information is in the form of an encoded digital message that accompanies the answer signal forwarded from the master station to the calling station. When the signal converter receives the answer signal, the signal is sent to the local telephone switching office and impulse metering is initiated in accordance with the encoded digital message that is latched in the signal converter and is used to generate impulses that are supplied to the local exchange via the supervisory transmission link. Once initiated, the impulse metering continues for the duration of the call, and is terminated automatically when the calling party hangs up or upon command from the control computer at the master station.
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