Automatisches Telefonschaltsystem

摘要

1,179,920. Automatic exchange systems. HITACHI Ltd., and NIPPON TELEGRAPH & TELEPHONE PUBLIC CORP. 19 Dec., 1967 [28 Dec., 1966], No. 57662/67. Heading H4K. In a system having a switching network through which paths are selected with the aid of a common marker, the latter M is seized on an outgoing call as soon as the first few digits have been received (via path T1) in a register sender ORS in order to try and set up a path T2 between the calling subscriber and a free trunk OGT in the relevant direction. If such a path cannot be found due to internal blocking then the marker is dropped. Whether or not a path is found, further digits are repeated over a link OSC between the register sender and the selected or a suitable free trunk OGT. When digit sending ceases the original path T1 is dropped, thereby freeing this path or parts thereof for immediate further selection and the marker is reseized in order to try and connect the caller to the trunk. If this cannot be done the call is abandoned. It is shown mathematically that this double use of the marker once with recycling (i.e. successive attempts at path finding using a different trunk at each attempt) before digit sending and once without recycling after digit sending leads to a lower blocking probability than the two known methods of using it viz. in either of the above two ways alone. It is also shown that the lowest blocking probability occurs when separate registers and senders are used.