| 摘要 |
<p>The additional facility can be applied to electronically managed telephone systems. In the central controller (ZST) of an exchange is a memory (SP) in which is stored details of each called number and call duration made by a subscriber (TN), if the latter has requested this facility. These details are then added to the subscriber's account. In the part of the memory allocated to the subscriber, commonly called numbers can be entered and reselected by the subscriber. To preserve secrecy about numbers called, should the subscriber wish it, but still be able to obtain a detailed account, an extra code can be keyed when selecting a stored number. If such a selection is made then only the address of the number selected is put into that part of the memory assigned to billing. As the number can be erased and re-entered at a different address of the subscriber's selection immediately after a call is completed the actual number called cannot be traced.</p> |
