| 摘要 |
A lead is connected to a positive battery potential, and via a changeover switch and a further lead. The potential is connected to a user point, e.g. a lamp, which in turn is connected to earth or the minus pole of the battery. A unit is connected between the potential and the lamp, which has two coupling components to cover two respective, spaced measurement points. The points are connected via leads to the control inputs of an operational amplifier. The amplifier is fed with current, and is earthed. - Resistances are provided for the amplifier, one of which is attached to a plate, and is connected to contact components so that current through the lead on which the unit is applied causes a voltage drop over the resistance. The unit constitutes a printed circuit, and also has a lead connected to an indicator, pref. in the form of a light diode. |
