In medical institutions, wandering elderly patients have become a problem, and the introduction of wandering sensing systems is underway. However, wandering sensing systems are known to affect wireless medical telemetry systems. In this research, we aimed to clarify the following two points. The first point is to visualize the signal of the wandering sensing equipment and the medical telemeter which influence by using the real time USB spectrum analyzer and to clarify the cause of the electromagnetic interference. The second point is to focus on the medical telemeter channel and to investigate how the wandering sensing system affects to which channel of the medical telemeter. With DPX real time display, we could observe three signals of wandering sensing system, main signal, out of band emission, instantaneous signal. Furthermore, the center frequency in the main signal of the wandering sensing system corresponds to 3000 series of wireless medical telemetry system. Those experiments suggested the possibility of electromagnetic interference when using the wandering sensing system and the wireless medical telemetry system (the channel numbers of 3000 series) simultaneously at relatively short distances (10 cm, 1 m, and 3 m). In addition to being the frequency band allocated for wireless medical telemetry systems, these channels are used in the wandering sensing system. Hence, it is necessary to consider possible electromagnetic interference problems.