为了完善通信系统的性能，除了主干电路外，还必须加入一些附加电路，如自动功率控制电路、自动温度控制电路和保护电路等等。

But to perfect the system performance, some accessorial circuits are necessary, such as automatic power control circuit, automatic temperature control circuit and protective circuit etc.

youdao

一般而言，永久性虚拟电路建在多个主干网交换机之间和交换机与网络信息流量大的设备之间。

Typically, permanent virtual circuits are set up between multiple backbone switches and between switches and devices with heavy network traffic.

youdao

目前承担微电子专业方向的主干课程：固态电子论、微电子器件与原理、集成电路设计，微电子工艺等课程。

It has key courses of microelectronics: solid-state electronic theory, microelectronic devices and principles, integrated circuit design, micro-electronics processing, etc.

youdao