Which of the following devices allows telephone calls to be made over an IP network such as the Internet instead of the ordinary PSTN system?

A.
IP phone

B.
Laptop

C.
IP camera

D.
Smartphone

Explanation:
An IP phone uses Voice over IP technologies, allowing telephone calls to be made over an IP network such as the Internet instead of the ordinary PSTN system. Calls can traverse the Internet, or a private IP Network such as that of a company. The phones use control protocols such as Session Initiation Protocol. Skinny Client Control Protocol, or one of the various proprietary protocols such as Skype. IP phones can be simple software-based Softphones or purpose-built hardware devices that appear much like an ordinary telephone or a cordless phone. Ordinary PSTN phones are used as IP phones with analog telephony adapters (ATA). Following is an image of an IP phone:

Answer option D is incorrect. A smartphone is a mobile phone that offers more advanced computing ability and connectivity than a contemporary basic feature phone. A smartphone is a mobile phone with advanced PC like capabilities. Blackberry and iPhone are the two most popular brands of smartphones. It allows the user to install and run more advanced applications based on a specific platform.

Answer option C is incorrect. An IP camera is a digital camera used for surveillance. It is unlike analog closed circuit television cameras can send and receive data through a computer network and the Internet. There are two types of IP cameras:

Centralized IP camera: It needs a central Network Video Recorder (NVR) to handle the recording, video and alarm management.
Decentralized IP camera: It does not need a central Network Video Recorder (NVR). Decentralized IP camera has built-in recording functionality and so. it can record directly to digital storage media.

Answer option B is incorrect. A laptop is a type of portable computer. It is designed for mobile use and small and light enough to sit on a person’s lap while in use. It integrates most of the typical components of a desktop computer, including a display, a keyboard, a pointing device (touchpad or trackpad, pointing stick), speakers, and often including a battery, into a single small and light unit.

Laptops are usually notebook-shaped with thicknesses between 0,7*1.5 inches (18-38 mm) and dimensions ranging from 10×8 inches (27x22cm, 13″ display) to 15×11 inches (39x28cm, 17″ display) and up. Modern laptops weigh 3 to 12 pounds (1.4 to 5.4 kg): older laptops were usually heavier. Most laptops are designed in the flip form factor to protect the screen and the keyboard when closed.