A variety of assistive devices are more developed according to the advances of the rehabilitation engineering. Disabled people are eager for the assistive devices to promote their life and quality in daily living. Although many manufacturers devote to the researches of the assistive devices, there is no open standard for the development of assistive devices. Multiple Master Multiple Slave (M3S) is an open standard. It is a simplified model which refers to the ISO-OSI (International Standard Organization-Open System Interconnection). In addition, the M3S aims at the safety of assistive devices, and it also describes the physical layer and network layer of the M3S reference model. M3S can apply system integration and allow disabled people to recover their physical abilities. During the development of assistive devices, safety is a critical issue that must be concerned, especially for the disabled user. The M3S system bus consists of digital signal transmission and real-time safety monitoring. The assistive devices, which connect to the M3S bus, transmit data by the CAN (Controller Area Network) protocol. Moreover, from the safety mechanism considerations, the M3S utilizes two additional lines and circuitry, i.e. KSL (Key Switch Latch) and DMS (Dead Man Switch). They can ensure the system status when users operate the assistive devices, and in this thesis, more emphasis will put on the development of KSL and DMS. M3S puts emphasis on both users’ safety and the data transmission of assistive devices. We design the general input and output adapters based on this concept. In addition to the adapters, we design some general input and output devices based on DSP (Digital Signal Processor) and combine these devices with the M3S adapter. Furthermore, we integrate the M3S adapters with the CCM (Control & Configuration Module) and implement the safety mechanism in the physical layer and the network layer. The input device is a head-controlled device, and the output devices are the motor circuitry of the powered wheelchair and the manipulator. Finally, we successfully utilize the control protocol (CAN) with the safety mechanism (KSL/DMS) to establish the system based on the M3S standard.