This allows the firms that find it cheapest to reduce their emissions to do so , leaving those for which cuts would be costlier to buy permits 这样一来，那些认为减少排放量是最经济的方法的企业就会甘之如饴；那些认为减少排放量不合算的企业则会购买配额。
But under some circumstances , such as bad terrain , where it is difficult to pave wire line , where an emergency happens and need to build network quickly , where information security is desired and where lower cost is desired , wireless dcs will be a better solution 但在某些场合，如地形条件不好、铺设电光缆存在困难；要求应急快速组网或临时组网；要求传输信道有一定保密性；因传输距离远，布线经济上不合算和维护成本高等，无线dcs系统将是一个更好的解决方案。
