| 摘要 |
<p>The invention refers to a signal generating device (2) for generating an electric signal, wherein the electric signal is a first logic signal when a signal generating path (21) carries an electric current, wherein the electric signal is a second logic signal when the signal generating path (21) does not carry an electric current and wherein the device (2) comprises (a) a first electric valve (V154) which is arranged in the signal generating path (21), (b) a first control unit (D8) which is connected to the first electric valve (V154) and which is adapted to control whether the first valve (V154) is open or closed, (c) a current detecting unit (R62, V45) which is arranged in the signal generating path (21) and/or is connected to the signal generating path (21) and which is adapted to generate a signal which depends on the size of the current which is carried by the signal generating path (21), (d) a second control unit (V46) which is connected to the current detecting unit (R62, V45) and to a gradually closable valve (V154) in the signal generating path (21) and which is adapted to limit the size of the current through the gradually closable valve (V154) by controlling this valve when the current in the signal generating path (21) increases, (e) a control arrangement (C3, A6, D8) which is connected to the first electric valve (V154) and which is adapted to close the first electric valve (V154) when the size of the current through the signal generating path (21) reaches or exceeds a threshold value for a time longer than a time interval of predetermined length.</p> |
