A fairly basic circuit (left as an exercise, but it's not difficult) can take the control voltage and output a constant current which is proportional to the voltage.
一个相当基础的电路(留作练习，不过并不难)处理控制电压并输出与电压成比例的恒流。
2
While Kibera has long been an obligatory stop for foreign dignitaries and film crews shooting movies such as The Constant Gardener, its addition to the tourist circuit has stirred debate.