We propose a safe operation architecture for a semi-autonomous remote control system for mobile robots using mobile communications. The currently used architectures are unable to cope with several issues: adapting to various types of mobile robots, maintaining a sufficient level of safety in an area of unstable communications, flexibly interpreting input from the controller side, and flexibly changing the control mode according to the robot's surrounding environment and the situation. To overcome these issues, we propose a safe operation architecture. Each functional unit is designed such that it is suitable for different types of mobile robots, and a range of control inputs from the controller side. Since the communication status between a base station and a mobile terminal is monitored by heartbeats, operation of the robot can be suspended safely when communication is lost. An initial system based on the proposed architecture has been developed using ROS (Robot Operating System). We conducted experiments with the system using delivery robots that served as the mobile robots. The experiments were performed in an outdoor field and used a 60 GHz mobile communication system.