| 摘要 |
PCT No. PCT/SE91/00911 Sec. 371 Date Jul. 23, 1993 Sec. 102(e) Date Jul. 23, 1993 PCT Filed Dec. 27, 1991 PCT Pub. No. WO92/13418 PCT Pub. Date Aug. 6, 1992.A method for signalling/communication within an entrance telephone system or similar, and a system utilizing the method, which facilitates selective communication from an entrance center or central unit (1) to a desired and addressed substation (5, 5', 5'') via a loop including at least two conductors, and which also facilitates entrance lock opening or a similar function from such a substation (5, 5', 5''). After approved addressing operation of the central unit (1) is performed by a visitor, the central unit (1) feeds work current to the loop (2, 2') joining the central unit (1) and connected substations (5, 5', 5''). By using a signal detecting means (6, 6', 6'') only the addressed substation (5, 5', 5'') then establishes a galvanical connection with the loop (2, 2') and the central unit (1). The central unit (1) performs thereafter generation of a ring signal, detection of "off-hook" or other statuses or signalling changes, and on detection of an incomplete reply, or terminated entrance telephone communication/function, the feeding of work current to the loop is interrupted. Address information from the central unit (1) is preferably transferred using a signalling type different from the signalling type whereby substations (5, 5', 5'') connected to the loop (2, 2') can influence the central unit (1) during an established connection in order to initiate entrance lock opening or other functions. |
