Definition of: ISDN (Integrated Services digital Network) an international standard for switched, digital dial-up telephone service for voice and data.

定义：ISDN(综合服务数字网络)，是一个国际转换标准，是为了语音和数据的数码拨号上网电话服务。

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The limited transmission rate available on the Public switched telephone network (PSTN) and on wireless networks presents a significant challenge to digital video communications.

这些应用对传输速率有限的公共交换电话网(PSTN网)和无线网络提出了重大挑战。

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However, VOIP differs from the usual phone services in that it sends calls as digital packets of information over data networks rather than relying on a dedicated circuit-switched network.

ECONOMIST: Taking the battle online | The