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A DAC converts digital signals into analog form as illustrated in Figure 13.2. Although one can interface a DAC to a regular output port, most DACs are interfaced using high-speed synchronous protocols, like the SSI. For more information about SSI, see Embedded Systems: Real-Time Interfacing to ARM® Cortex™-M Microcontrollers, 2020, ISBN: 978-1463590154. The DAC output can be current or voltage. Additional analog processing may be required to filter, amplify, or modulate the signal. We can also use DACs to design variable gain or variable offset analog circuits.
Sound exists as varying pressure waves that are created when a physical object moves, vibrating the air next to it. These air pressure waves travel through the air in all directions at about 343 m/sec. Sound can also be generated in water, where it travels at 1484 m/sec. Our ears can sense sounds from 20 Hz to about 20 kHz. In other words, the pressure wave must be oscillating faster than 20 Hz and slower than 20 kHz for us to hear it. See Figure 13.4.
RBAC grants access based on a user’s role and implements key security principles, such as “least privilege” and “separation of privilege.”. Thus, someone attempting to access information can only access data that’s deemed necessary for their role.
Access control is a method of guaranteeing that users are who they say they are and that they have the appropriate access to company data. At a high level, access control is a selective restriction of access to data. It consists of two main components: authentication and authorization, says Daniel Crowley, head of research for IBM’s X-Force Red, ...
MAC is a policy in which access rights are assigned based on regulations from a central authority.
A number of technologies can support the various access control models. In some cases, multiple technologies may need to work in concert to achieve the desired level of access control, Wagner says.