| 摘要 |
To ensure that the transmission qualities on internal connections and external connections are approximately the same, insertion losses must exist for internal and external connections which are substantially greater for internal connections than for external connections. Switchover from one attenuation value to the other in the subscriber circuits or exchange circuits depending on the connection type entails undesirable expenditure. Hitherto implemented even distribution of the attenuators between transmission time and reception time results in inadequate utilisation of the modulation range of the equipment used for digital/analog or analog/digital conversion. Therefore, according to the invention, the subscriber circuits (TS1 to TSn) have an attenuator (Di) in their reception path on the analog side whose attenuation value is equal to the overall insertion loss for internal connections and the exchange circuits (AS), in their part associated with the outgoing transmission direction, contain an attenuator (DE) whose attenuation value corresponds to the overall insertion loss for external connections and, in their part assigned to the incoming transmission direction, contain an amplifier which can compensate for the attenuation of an attenuator in the subscriber circuit apart from the predefined overall insertion loss for external connections. <IMAGE>
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