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Abstract

A switching arrangement for establishing a signal path between any one of a plurality of first ports and a common port and for varying the attenuation of at least one of the ports comprises in the signal path of each attenuatable port a first switching element and attenuating circuitry connectable by further switching circuitry across the first switching element, the first switching element constituting the sole series element in that path. The attenuating circuitry comprises a resistive network and the further switching circuitry comprises second switching elements connected to respective ends of the first switching element and to respective points of the resistive network for introducing one of a number of resistive states into the signal path. The relevant port is isolated either by switching the first and second switching elements OFF, or by switching OFF the first element and also a third switching element connected in series between a second switching element and that end of the first switching element which lies downstream in the signal flow path. The switching elements may be FETs and the switching arrangement may take the form of a single-pole, double-throw (SPDT) switch or a switch of any number of 'poles' or 'throws'.

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First Claim