Features: 1) Monitor 4 or 8 lines of phone working state separately 2) Start charging by means of polar-reverse, manually and automatic delay 3) Supply incoming-call free or charge 4) Store up to 50,000 phone bills, and daily records of the latest 366 days 5) Powerful statistic and print function 6) Supply multi-operator mood 7) Transmit tariff rate, clock, initialization and upgrade program rapidly by serial communication tool 8) Rechargeable battery lasts up to 8 hours 9) Each phone line has a remote display for a caller 10) Realize wireless access by wireless conversion pool