调制解调器：
调制解调器是一种硬件网络设备，其基本功能是将数据转换为信号。调制解调器很重要，以便拥有互联网接入。调制解调器有两种类型：
1. 内部调制解调器：
顾名思义，内部调制解调器是计算机内部的内部部件。它通常与计算机一起提供，并且也是预装的。内置调制解调器的最大优点是它使用计算机的电源运行，不需要额外的电源即可工作。
2. 外部调制解调器：
外部调制解调器与内部调制解调器相似，因为它也允许访问 Internet。外部调制解调器是计算机的外部部件。当计算机无法在其中安装内置调制解调器时，可以使用它。调制解调器通常通过串行或 USB 电缆连接到计算机，并且还需要外部电源才能运行。
内部和外部调制解调器之间的区别：
| S.No. | Internal Modem | External Modem |
|---|---|---|
| 1. | It has built-in UART. | It doesn’t have built-in UART. They use the computer’s serial port as UART. |
| 2. | Its Price is low as compared to external modem. | It is comparatively high in price. |
| 3. | For internal modem, user doesn’t need to buy any external accessories. | In an external modem, RS232 interface cable has to be brought. |
| 4. | It is hard to transfer the internal modem to another computer. | The external modem can be moved easily. |
| 5. | The internal modem is powered by PC. | The external modem needs external power supply. |
| 6. | It is present inside the computer. | It is present outside the computer. |
| 7. | It can insert into a vacant expansion slot. | It cannot come into the expansion slot. |
| 8. | No holder case is required. | Holder case is required. |
| 9. | It is incompatible with different kind of PCs. | It is compatible for all kind of PCs. |
| 10. | The user is unable to see the status of the modem directly. | The user can check the status of the modem directly. |