The precautions of the interference caused from poor isolation outside MT8820B/C, i.e. between UEs and RF cables, should be considered, Especially, in case of using MT8820B/C Parallel Phone Measurement (PPM) configuration which can do 2port-measurement independently by single unit, the interference problem may be occurred easier than 1 port/1 unit configuration since the UEs and/or RF cables tend to be located closely in the production line. Moreover TDD (Time Division Duplex) mode in TD-SCDMA, and TD-LTE technology tend to have the interference problem since TDD uses the same up and down frequencies. But there is also a possibility that FDD mode in WCDMA, GSM, C2K, and LTE FDD while the same frequency in a test is used between UEs. Meanwhile the MT8820C internal isolation between Phone 1 and Phone 2 is at least 138 dB min, which is enough against the interference.