spare circuit

基本解释

Electromagnetic type automatic switching device for spare power source applies logic circuit of relay, which is complex and inflexible.
为改善电磁型备用电源自投装置接线复杂、功能僵化、误动等缺点，提出了一种新型的微机型备用电源自投装置。
You can use spare sockets to try out different discrete component values. Just keep the ones that are spec-compatible in the circuit, and get the job done.
您可以使用备用插座，测试不同的分立元件值。只须维持规范的是在电路兼容，以及完成这项工作。
www.tech-domain.com
It describes spare time activities of digital circuit teaching and the effect on the interest of electronic activities and educate student to become qualified persons.
阐述了数字电路教学的校外课外开展活动的情况，在电子兴趣活动以及在培养学生成才方面的作用。