H - Electricity – 04 – K
Patent
H - Electricity
04
K
344/12, 325/19,
H04K 1/00 (2006.01) G07C 9/00 (2006.01)
Patent
CA 1242500
ABSTRACT: The circuit arrangement in a communication system which is protected by subscriber-specific passwords com- prising a memory (1) which contains all the possible pass- words and a comparator which compares each received pass- word with the memory content comprises in addition a mono- stable delay circuit (3) with a subsequent logic combining gate (6), which are connected to the output of the compar- ator (2) via an input gate (5). The monostable delay cir- cuit and the logic combining gate are so prepared in depen- dence on the presence of an energizing signal applied to a special input (C) that when there is non-agreement between the received and the stored passwords the monostable delay circuit (3) starts and during operation inhibits the logic combining gate (6), whilst when there is agreement the logic output gate (6) is enabled. Such a circuit arrange- ment can be provided before each selector stage of a switching system of before each accessible channel of a mobile radio system. To protect the arrangement from mech- anical intervention, the circuit arrangement is provided unaccessible on a support 7 and is surrounded by an unaccessable envelope.
475999
N.v.philips'gloeilampenfabrieken
Van Steinburg C.e.
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