如果数字化的内容是使用一些DRM方案保护的，可能还需要票据交换服务。

If digital content is protected using some DRM solution, a clearing house service may be required.

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SSL使用数字证书为加密、服务器验证以及客户机验证(可选)提供密钥交换服务。

SSL USES digital certificates to exchange keys for encryption, server authentication, and optionally, client authentication.

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网络控制的概念被扩展到了让数字交换机与数据库（称为服务控制点）和信号处理系统（智能外设）通信。

The concept of network control was extended to let digital switches communicate with databases (known as Service Control Points) and signal processing systems (Intelligent Peripherals).

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