Internal modems are installed inside the computer case. They connect to the computer's motherboard using a variety of interfaces, including PCI, ISA, or USB. Internal modems are typically less expensive than external modems, and they can provide better performance because they are not subject to the same interference as external modems. However, internal modems can be more difficult to install, and they may not be compatible with all computers.
External Modems
External modems are connected to the computer using a USB or serial port. They are typically more expensive than internal modems, but they are more portable and can be used with any computer that has a USB or serial port. External modems are also less likely to interfere with other devices in the computer, and they can be easily replaced if they fail.
Types of Modems
There are two main types of modems: analog and digital. Analog modems transmit data using a continuous signal, while digital modems transmit data using a series of discrete pulses. Digital modems are typically faster and more reliable than analog modems.
Analog Modems
Analog modems were the most common type of modem in the early days of the Internet. They use a variety of modulation techniques to encode digital data onto an analog signal. The most common analog modulation techniques are frequency shift keying (FSK), phase shift keying (PSK), and quadrature amplitude modulation (QAM).
Digital Modems
Digital modems are the most common type of modem today. They use a variety of digital modulation techniques to encode digital data onto a digital signal. The most common digital modulation techniques are binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), and orthogonal frequency division multiplexing (OFDM).
Comparison of Analog and Digital Modems
| Feature | Analog Modems | Digital Modems |
|---|---|---|
| Speed | Slower | Faster |
| Reliability | Less reliable | More reliable |
| Cost | Less expensive | More expensive |
| Portability | More portable | Less portable |
| Compatibility | Less compatible | More compatible |
Choosing a Modem
When choosing a modem, you need to consider the following factors:
* Speed: The speed of the modem is measured in bits per second (bps). The higher the bps, the faster the modem.
* Reliability: The reliability of the modem is determined by its ability to maintain a connection without dropping out.
* Cost: The cost of the modem can vary depending on the features and speed of the modem.
* Portability: The portability of the modem is important if you need to use it with multiple computers.
* Compatibility: The compatibility of the modem with your computer is important. Make sure that the modem has the appropriate interface for your computer.
By considering these factors, you can choose the right modem for your needs.