The resistor (r) must be large enough to limit the current through the diodes to prevent damage to the diodes.
电阻器(R)必须足够大，以限制流过二极管的电流，使之不会损坏二极管。
The resistor (R) is used to limit the current through the diodes (D1 and D2).
电阻器（R）用来限制流过二极管（D1和D2）的电流。
In this case, the series resistor should be placed as close to the relay as possible to limit the current when charging the cable capacitance.
在这种情况下，串联电阻就应该尽量靠近继电器，以限制电缆电容充电时的电流。
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