In order to improve the ringing method of telephone used in power systems a type of selective calling device using audio frequency has been developed .

为了使电力系统 通信设备的呼叫装置更加使用方便工作可靠，我们研制了以按键 电话机发出双音频呼叫 信号进行选择接收的 音频选号装置。

Methods By using many kinds of technology such as computer website telephone short message and the video frequency etc. we establish a integrative electron platform for customers .

方法采用计算机、网站、 电话、短信、 视频等多种技术，建立一体化的客户服务电子平台。

The test methods for 60-channel symmetrical cable carrier telephone equipment high - frequency channel

GB/T4770.3-1984对称电缆60路载波 电话设备主要性能的测试方法

The dielectric resonators illustrated with examples have been applied to duplexer for the cellular mobile telephone and frequency stabilizer for oscillator .

最后举例说明介质谐振器在蜂巢式便携 电话中的双工器及稳 频振荡器方面的应用。

Long-distance control of telephone does not require special wires distribution and does not take up wireless frequency resources . Electromagnetic pollution can thus be avoided .

电话远程控制不需进行专门的布线，不占用无线电 频率资源，还可避免电磁污染。

With the quantity unceasingly grows telephone facsimile modem and computer are demanding more and more high to the band width to transmit the Gbit digitized information ( video frequency picture constructs model procedure as well as data and pronunciation and so on ) .

数量不断增长的 电话、传真、调制解调器和计算机，它们对带宽的需求越来越高，以用来传送吉比特数字化信息（ 视频、图像、建模程序以及数据和语音等）。

For the requirements of the signal-to-noise ratio of lower in part of telephone channel the algorithm to convergence in the time domain and frequency domain step by step .

针对部分 线路上 语音信噪比较低的实际，引入谱熵进行分级检测，将算法在时域和 频域逐级进行收敛。

As an appurtenance of telephone this remote alarm equipment is used to be an alarm for private house protect based on the transmission of DTMF ( Dual Tone Multiple frequency ) .

本文设计的 电话远程报警器是基于DTMF（双音 双频 信号）传输、作为 电话的附属物而开发的家庭远程报警系统。