1. 网络电话(VoIP)：
VoIP 代表互联网协议语音，也称为 IP 电话或互联网电话或宽带电话。简单来说，它指的是 Internet 上的电话服务。该技术允许使用宽带互联网连接而不是普通电话线进行语音通话。它用于通过 Internet 协议 (IP) 网络传输高范围语音通信以及多媒体会话，这就是它被称为 IP 语音的原因。现在，它是在人与人之间传递声音的最有效方式之一。
在 VoIP 中，互联网被用作电话呼叫的传输介质，通过使用(互联网协议)IP 以数据包的形式发送语音数据。它将实时语音信号从源 IP 地址传输到目标 IP 地址。目前，互联网协议语音 (VoIP) 是早期/传统电话服务的可靠且具有成本效益的替代方案之一。
2. 公共交换电话网(PSTN)：
PSTN 代表 Public Switched Telephone Network 也称为传统电路交换电话网，以前它仅称为公共电话网。 PSTN 是指允许不同站点的人之间进行语音通信的电信网络。 公共交换电话网络使用一种古老的技术，它使用铜线传输模拟语音信号。它由当地、国家和国际航空公司运营。
公共交换电话网络基于电路交换概念。当在两部电话之间建立专用路径时，它们之间就建立了电路。所有固定电话都是公共交换电话网 (PSTN)。
VoIP 和 PSTN 的区别：
| S.No. | VoIP | PSTN |
|---|---|---|
| 01. | Voice over Internet Protocol uses packet switching. | Public Switched Telephone Network uses circuit switching. |
| 02. | In VoIP, only an internet connection is required. | In PSTN, dedicated lines required from telecom company. |
| 03. | No dedicated path required between sender and receiver. | Dedicated path required between sender and receiver. |
| 04. | One VoIP lines require 100 kbps. | One link typically supports 64 kbps. |
| 05. | In VoIP, it acquires and releases bandwidth as it is needed. | Bandwidth is reserved in advance it requires as each line is 64 kbps. |
| 06. | In VoIP, Cost is not dependent on distance and time. | In PSTN, Cost is based on distance and time. |
| 07. | Extensions is a standard feature of VoIP. | Extensions requires extra costs in PSTN. |
| 08. | VoIP provides consistent voice quality but depends on bandwidth. | PSTN provides consistent voice quality. |
| 09. | Call waiting, call forwarding, call transfer are standard features of VoIP. | Call waiting, call forwarding, call transfer are usually standard features in PSTN but sometimes it costs extra for this. |
| 10. | Scalability and upgrades requires improved internet bandwidth. | Scalability and upgrades requires substantial hardware additions. |