发明名称 ANORDNING VID INKOPPLING OCH URKOPPLING AV EN RINGSIGNAL TILL EN UPPRINGD ABONNET
摘要 The present invention relates to an apparatus in ringing signalling to a called subscriber. Connection and disconnection of the signal takes place with the aid of the apparatus. The problem solved by the invention is that of current transients being generated on disconnection of the signal, these transients causing a disturbing clicking noise in the engaged telephone of a subscriber in a neighbouring channel. The apparatus solving the problem includes a two-way switching circuit (10) connected in series with an AC voltage generator (2), said circuit disconnecting the AC voltage to a bell (1) when the current through the bell has its zero crossing, and a discharge circuit (11) for discharging the bell before it is connected via a relay (3) to a SLIC circuit (4), such that the voltage across the bell is within the SLIC circuit voltage interval when the relay (3) connects the bell to the SLIC circuit (4), which occurs when said signal is disconnected. By this arrangement an overvoltage protector (7) connected to the SLIC circuit (4) is not triggered, and the circuit is not subjected to any current transient which can cause disturbing clicking noises.
申请公布号 SE8703890(L) 申请公布日期 1989.04.09
申请号 SE19870003890 申请日期 1987.10.08
申请人 ERICSSON TELEFON AB L M 发明人 LOEFMARK B G
分类号 H04M3/02;H04M19/02;(IPC1-7):H04M3/18 主分类号 H04M3/02
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