## 1 Introduction  
Industry 4.0 is considered to be the fourth industrial revolution and is characterised by smart manufacturing. It is a comprehensive and flexible system covering digital manufacturing technologies, network communications, computer technologies, automation technologies and many other areas. The fundamental of implementation is based on digital design and simulation, highly automated production, data from production processes and management of production processes, creating the whole process to gain knowledge from the production. On the other hand, Industry 4.0 is based on cyber-physical systems (CPS) using computing, communication and control technologies in close cooperation to achieve real-time intelligent manufacturing systems, dynamic control and information services. IoT, Big Data, AI, Augmented Reality, Simulation, Horizontal and Vertical Integration, Additive Manufacturing, Autonomous Robots, Cloud Computing and Cybersecurity are considered to be the key Industry 4.0 technologies [1]. Figure 1 shows a diagram of Industry 4.0 with the mentioned technologies. Deploying all the Industry 4.0 technologies and moving the enterprise to the Smart Factory level is costly, time-consuming and personnel intensive. Large companies have adopted strategies for introducing digitisation into production, but the problem is represented by SMEs with a lack of capital and staff. Surveys show that SMEs are largely unaware of the need to introduce digitalization into production. In the future, such companies may lose their place in the market, as they will lose their competitiveness compared to large companies and small- and medium-sized digitised companies. If SMEs were to implement at least some of the key Industry 4.0 technologies, they could more easily sustain themselves in the market, speed up production and increase production capacity. This brings us to the main research question: Which key Industry 4.0 technologies should SMEs deploy? This could lead to a change in the adoption of business digitisation strategies in the future. In this article, we deal with the answer to this question. Research articles mainly focus on selected Industry 4.0 technologies that they describe as important from their perspective, which creates the space for this research. In our paper, we have focused on all the important Industry 4.0 technologies, and through a literature overview, we have identified the necessary attributes with a focus on SME. The importance of digitalisation for SMEs has also been declared by the European Commission, which has launched projects and conferences to support SMEs in the field of digitalisation. The European Commission considers Artificial Intelligence to be the most important element of the Fourth Industrial Revolution, especially for small- and medium-sized enterprises. In second place in terms of importance and benefit, they consider Big Data analytics, and advocate a Business-to-Business strategy for implementing Big Data into practice. The European Commission sees huge potential in small- and medium-sized enterprises and emphasises the importance of transforming them into digital enterprises. With the deployment of AI in key areas, GDP is estimated to increase by around 1.8% by 2025, and in the longer term to result in a cumulative increase of 13.5% by 2030, depending on region and industry [2]. AI is likely to have the biggest positive impact on manufacturing--especially IIoT, mobility and smart healthcare. Achieving the best possible results will depend on harnessing the full potential of AI in SMEs. This paper highlights the following:  
1. identification of the necessary attributes of Industry 4.0 to move the SME to a level close to the Smart Factory,
2. highlighting the need for digitisation for SMEs,
3. proposing devices meeting the identified attributes of Industry 4.0 and their prospective use in SME. Figure 1: Industry 4.0 scheme. In Section 2, we describe Big Data and AI as important tools that the European Commission considers to be the most important attributes of digitalisation.