Access unit for local area network

Details Access unit for local area network Access unit for local area network

1990-10-02

1993-01-12

Pellinen, A. D.

Electrical transmission or interconnection systems

Switching systems

Switch actuation

34082505, 34082518, 370 8515, H04J 302

Patent

active

051792915

ABSTRACT:
An access unit for a local area network with loop topology includes a pair of connectors, a relay circuit, a pair of transformers, a direct current signal extraction circuit, a constant current circuit, a controller, and a coil. With the above arrangement, when a workstation connected to the access unit generates a composite signal having a DC signal, used for driving the relay circuit, superposed onto an AC signal for data transfer, only the DC signal component is extracted by the direct current signal extraction circuit to be inputted into the controller of the access unit. The relay circuit of the access unit is then operated. Thus, the signal outputted from the workstation, the composite signal having the DC signal superposed on the AC signal, is applied to the concentrator, so that the DC signal contained within the composite signal activates the relay contact in the concentrator. The DC signal superposed on the AC signal is outputted from the workstation and accordingly activates both the relay contact in the access unit and the relay contact connected thereto in the concentrator.

REFERENCES:
patent: 4567482 (1986-01-01), Dolsen et al.
patent: 4701630 (1987-10-01), Annunziata et al.
patent: 4862158 (1989-08-01), Keller et al.
patent: 4905230 (1990-02-01), Madge et al.
patent: 5034738 (1991-07-01), Ishihara et al.

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