浅谈计算机网络电话通信系统的电话终端探究

电话通信作为主要的通信技术，目前得到人们的广泛应用，在社会发展过程中起到了举足轻重的作用。随着社会经济的不断发展，人们对电话通信技术的要求也逐渐提高，比如信号的稳定性，通话质量要求的提升，以及数据量的不断增加，都使得电话通信技术的发展面临重大挑战。计算机网络电话通信技术的发展，很大程度上改善了电话通信技术的效果，促进了电话通信技术的快速发展。本文就点算计网络电话通信系统的电话终端进行探究，指出了网络电话通信技术设计思路以及电话终端实现方法。     

Internet电话技术及其应用前景

文章介绍了Ｉｎｔｅｒｎｅｔ上话音传送技术的几种实现方式及电话网关的组成，预测了Ｉｎｔｅｒｎｅｔ电话市场的前景及其将对传统电话业务的影响。     

交换机与电话技术研究探索

从电话的发明使用就伴随着交换机的诞生，交换机是电话网络中的心脏，电话技术的革新促进着交换技术的革新，交换机的使用促进了电话的普及使得电话应用更加广泛，直至今日交换技术终于走到了主导地位，从电话行业到更广阔的通信领域。     

促进市话发展的本地个人手持电话系统—PAS

在蜂窝移动电话飞速发展和普及的今天，谁不想拥有一部手持移动电话，谁不想随时随地、随心所欲地拨打电话。但蜂窝移动电话较高的通话费用让许多人，特别是工薪阶层望而却步。随着无线通信技术日新月异的发展，有心的技术专家终于找到了既能在一定范围内随时随地手持拨打...     

一种微机控制电话指挥系统

本文介绍一种微机控制电话指挥系统。该系统曾在广东省核电站事故应急演习中成功地发挥了非常重要的作用，本文仅对该系统的功能，系统的组成及所采用的一些主要技术原理作简要介绍。并以省核电站事故应急通知系统作为一个应用实例来叙述。     

INtessTM—C＆T9005测试系统的安装调试

本文介绍了ＩＴｔｅｓｓＴＭ－Ｃ＆Ｔ９００５１２测试系统的特点，及针对几种型号交换的安装调试技术。     

WLAN IP电话：中国特色

IP电话已占据整个市场，不再被视为一项新兴技术，它往往与来自多个厂商的IP-PB系统捆绑在一起。同时，由于WLAN标准的出台，企业网络可以通过扩容部署来不断提高对服务质量的支持。这两项技术的自然发展使得WLANIP电话应运而生。     

农村电话用户市场调查与分析

受中国电信委托、原邮电部经济技术发展研究中心在全国进行一次农村电信市场调查，以了解当前农村通信市场发展潜力，本文公布了此次调查的结果，从经济能力、资费和潜在市场等方面提出了发展农话的建议 。     

计算机电话技术突飞猛进

传统的公用电话网（PSTN）与数据通信网络朝各自的方向发展，它们之间的藩篱制约了它们的融合。随着计算机电话（C）技术和通信技术的发展，计算机通信网与电信网的结合越来越紧密，它们之间的技术鸿沟逐渐被填平。同时，计算机技术与电信技术的融合也促进了电信和数据通信应用的发展，智能同及近年兴起的网络电话（IPPhone）不但得益于CT技术，也必将促进CT技术的突飞猛进。CT技术简单地说，CT技术就是一种计算机系统与电话系统相结合的技术。它起源于80年代中期，开始只能进行简单的话务处理和提供有限的服务。到了90年代，随着语…     

第十四讲 免提电话（三）

第十四讲　免提电话（三）邮电部第一研究所电话机研究室编者按免提电话分三讲介绍，到此告一段落。我们想告诉读者的是，目前市场畅销的免提电话在使用上还存在一定的局限性，免提通话效果并不完全令人满意，音控防鸣技术尚有待改进。４免提电话的测试方法４．１响度评定...     

GaAs m.a.o.s.f.e.t. memory transistor

A new non-volatile memory device is reported. This device is a GaAs m.o.s.f.e.t. with charge storage in the gate in which is a double oxide structure of aluminium oxide and GaAs native oxide, both oxides are grown anodically. The fabrication of the device is described and the results of initial measurements on the charging and charge retention properties are presented.     

Switching in m.i.s.m. and m.i.s.i.m. structures

Switching has been observed in metal?thin-insulator?n-p+ structures, where the thin insulator is SiO2, or polycrystalline silicon. In this letter two alternative structures are discussed in which the n-p+ junction is replaced by a Schottky barrier. In the second device proposed two thin-insulator structures back-to-back are shown to exhibit bidirectional switching.     

U.H.F. low-noise GaAs m.e.s.f.e.t. amplifier for colour t.v. broadcasting translator

Low-noise amplifiers for u.h.f. colour t.v. broadcasting translator use have been successfully developed by using 1 ?m gate GaAs m.e.s.f.e.t.s. The obtained performances revealed that a GaAs m.e.s.f.e.t. has low-noise and low intermodulation distortion characteristics, even in the 500?800 MHz frequency range, compared with a Si bipolar transistor.     

Avalanche noise in GaAs m.e.s.f.e.t.s

Instabilities in the d.c. characteristics of GaAs m.e.s.f.e.t.s for drain to source voltages greater than 4 V. believed to be due to reloading of traps in the interface between active layer and bulk material, or gunn-domain formation, seem to have their origin in avalanche breakdown of the back diode under the drain contact. Microplasma switching, vertical to the active layer, strongly modulates the drain current producing large broadband noise power.     

Power m.o.s.f.e.t. linear h.f. amplifiers

N-channel silicon m.o.s. transistors for h.f. power applications have been fabricated which are optimised for linear amplification. These devices exhibit 2 W output power and 11 dB power gain at 630 MHz in class-A operation. The intercept point for third-order intermodulation distortion is 48dBm, which is considerably more than the same data obtainable with bipolar transistors.     

Performance of GaAs power m.e.s.f.e.t.s

Power performance results at 4 GHz are summarised for GaAs m.e.s.f.e.t.s ranging in size from 4 to 16 mm gate periphery. A double-chip 16 mm unit operated at 24 V source-drain bias produced 13.5 W with 3 dB gain and 10.7 W with 8.1 dB gain. Although lack of perfect power and gain scaling is observed, the degradation in output power of the 16 mm devices was only 1 dB compared to the smaller devices.     

Noise behaviour of the m.o.s.f.e.t. at v.h.f. and u.h.f.

The optimum noise figures of an m.o.s.f.e.t. at u.h.f. and at pinch-off are calculated using a simplified equivalent circuit. The noise parameters are also determined experimentally. Theory and experiment are shown to be in good agreement. Noise parameters of the m.o.s.f.e.t. for the frequency range 0.1?0.8 GHz are given.     

Substrate conduction in GaAs m.e.s.f.e.t.s

Substrate currents in a gateless GaAs m.e.s.f.e.t. have been measured at d.c, 0.9 MHz and 2 GHz. The results are consistent with the assumption of substrate conduction at high frequencies and active-layer conduction alone at low frequencies.     

Noise calibrator for v.h.f. and u.h.f. field-strength-measuring receivers

A simple noise generator, based on a semiconductor diode of the Zener type and suitable for use in the frequency range 30?900 MHz, can be used to check both absolute gain and noise performance of sensitive receivers.     

Substrate dependence of InP m.e.s.f.e.t. performance

There is evidence to suggest that Fe outdiffuses, during the growth, into the epitaxial films prepared by vapour-phase epitaxy at 650°C. Field-effect transistors on Fe-doped material show substantial looping that was absent on Cr-doped material and exhibit about 2 dB worse noise figure at about 7 GHz. Experiments with low 1015 S-doped InP grown on Sn-, Cr- and Fe-doped substates indicate that such outdiffusion is typically about 5 ?m. Saturation velocity levels in the m.e.s.f.e.t. channel are about 1.7 × 107 cm/s and 1.3 × 107 cm/s, associated with Cr and Fe doped substrates, respectively.