# Design and Implementation of a Smart Intercom System through Web Services on Web of Things
## 2 Related Research
If the username and password are verified in the internet database, the door can be opened successfully. If the verification is unavailable, a buzzer will sound and send an SMS alert to the homeowner to enhance home security [18]. Security is the main issue in a home. Letting the right people, such as family, into the house and keeping intruders out is very important. Studies are using a facial recognition door lock system; the visitor looks at the camera, and the electromagnetic lock will unlock the door if the image exists in the database. Otherwise, an alarm message will be sent to the owner in the form of an email [19]. There is a security door lock system based on embedded system technology, which uses a camera and a keypad to identify visitors and residents and can notify the homeowner that only authorized individuals have permission to enter the door [20]. These arguments are intended to address the issue of people with access rights being able to easily and securely open and close door locks without losing or duplicating door keys, causing security problems in controlled areas. This is different from the purpose of this paper, which is to allow the occupants to know that someone is visiting even if they are not home and to communicate with the visitor at any place so that the thief cannot determine whether someone is home through the intercom used. Access control systems can also be operated from a cell phone using an Android application, which is controlled by facial detection and recognition according to a camera installed outside the door. The system can also control all the appliances by the user's voice [21]. In addition, the system can allow users to control home appliances through instant messaging software without the need to install an app on the smartphone [22]. There are also embedded systems and programming languages working with motors and sensors to develop a prototype system for controlling air conditioners and contacting the user through a chatbot. One of the advantages of a chatbot for controlling air conditioners is that it is easy to use since the user interface is designed to be very user-friendly and \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Type** & **Network** & \begin{tabular}{c} **Connection** \\ **Method** \\ \end{tabular} & **User** & \
\begin{tabular}{c} **Device** \\ **Location** \\ \end{tabular} &
\begin{tabular}{c} **Operation** \\ **System** \\ \end{tabular} \\ \hline Traditional intercom [1] & P2P & Wired & Resident/Visitor & Fixed & Dedicated system \\ VoIP intercom [11, 12] & IP network & Wired/Wireless & SIP user & Fixed/Mobility & General system \\ Mobile intercom [15] & IP network & Wireless & Apps user & Mobility & General system \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison list of the properties of three types of intercoms. can be used anywhere, anytime, as long as there is an internet connection [23]. The voice system can also be used for home appliance control, entertainment systems, lobby facility monitoring, and home security [24]. Instant messaging software has replaced the function of making phone calls as a tool for talking to friends and is the primary tool for communicating with customers in business. Chatbots are an essential feature of instant messaging platforms that deliver customers' information and replace human response efforts. An embedded system is a computer system with real-time computing capability, usually to perform some specific tasks. Due to its convenience, it is widely used in various research, and many papers also mention that embedded systems can be remotely monitored for research. With the integration of embedded systems, instant messaging platforms, and WoT technologies, the residents using these technologies can control door locks, cameras, and buzzers through instant messaging software and use chatbots to drive embedded systems. The system also hopes to integrate these technologies to provide visitors with the possibility to talk directly to residents through the integration of the web services.