摘要:
A telecommunications system for information having a variable structure. The system uses at least one frequency channel for transmitting each second N.sub.T transmission packets to subscriber arrangements. These packets are formed by n.sub.t bits and are allocated to subscriber arrangements themselves producing 1/Ts information packets of n.sub.s bits per second. The system includes a time-division multiplex circuit (10) for multiplexing the information signals coming from subscriber arrangements (SPA1, CIA2, . . . , SPAm . . . ) and, alternatively, a demultiplex circuit (28) for distributing the time-division multiplex information signals to subscriber arrangements. Interleaving circuits are coupled to the multiplex circuit for inserting, into an allocated transmission packet, bits of different information packets allocated to the same subscriber arrangement. De-interleaving circuits coupled to the demultiplex circuit perform the reverse operation.
摘要:
A plurality of subscriber units are connected to at least two transceiver stations for exchanging information in a time division multiple access mode, in which traffic time intervals are allocated in rotation to a variable number C of channels, where C is dependent on the number and type of units to be connected. T intervals plus one control time interval form a frame, where T is mutually prime with respect to the numbers 2 through C.sub.MAX. M frames form a superframe, where M is the lowest common multiple of the numbers 1 through C.sub.MAX.
摘要:
A magnetic resonance signal of a volume of interest within an object is acquired by placing the object in a magnetic field and the application of three successive steps. The first step comprises an rf selective 90.degree. pulse of frequency f.sub.x applied in the presence of an x-gradient magnetic field to select a slice. The magnetization of the slice is then inverted. In the second step an rf selective 90.degree. pulse of frequency f.sub.y is applied in the presence of a y-gradient magnetic field to excite a strip of the slice, in the third step an rf selective 180.degree. pulse of frequency f.sub.z is applied in the presence of a y-gradient magnetic field to refocus the magnetization of a region of said strip. The resulting free induction signal is derived solely from said region.