Patent ID: 7003048

Claim:
A communication arrangement ( 1 ) by which data (DA) can be transmitted to a transponder ( 2 ), comprising: a data source ( 5 ) for providing the data (DA), a carrier signal generator ( 6 ) for generating a carrier signal (CS), modulation means ( 7 ) for modulating the carrier signal (CS) in accordance with the data (DA) to produce a modulated carrier signal (CSM), and transmitting means ( 8 ) having a nominally constant input resistance ( 9 ) responsive to the modulated carrier signal (CSM) wherein the modulation means ( 7 ) includes an output resistance ( 10 ) which together with the input resistance ( 9 ) of the transmitting means ( 8 ) forms a resistance network ( 11 ), characterized in that: the output resistance ( 10 ) can be changed and resistance change means ( 25 ) are used for changing the output resistance ( 10 ) of the modulation means ( 7 ) in accordance with the data (DA), wherein the changeable output resistance ( 10 ) of the modulation means ( 7 ) can be combined from a first partial resistance ( 12 A) and a second partial resistance ( 12 B) and in that switching means ( 15 , 16 , 19 and 20 ) are provided for connecting the two partial resistances ( 12 A, 12 B) in parallel, and wherein at least one of the two partial resistances ( 12 A, 12 B) is realized by means of at least one driver ( 26 , 27 ; 39 , 40 , 41 , 42 ), while the driver ( 26 , 27 ; 39 , 40 , 41 , 42 ) has a transistor ( 28 , 29 , 33 , 34 ; 44 , 46 , 48 , 50 ) on its output side, wherein said transistor can be driven to a switching operation in which a turned-on transistor ( 28 , 29 , 33 , 34 ; 44 , 46 , 48 , 50 ) forms a basic resistance connected in a parallel combination to the first or second partial resistance ( 12 A, 12 B).