Features: 1) Four billing initialization modes: polar-reverse, 16kHz pulse signal, manually and delay automatically charge 2) Pre-payment option, including sum set and payment calculation after a call 3) In-coming-call free or charge 4) Powerful statistic and print function 5) Stores up to 3,000 phone bills, daily records for the latest 100 days 6) Multi-operator mode 7) Transmit tariff rate, clock, initialization and upgrade program rapidly by Serial Communication Tool 8) Built-in Rechargeable battery lasts up to 8 hours 9) Each phone line has a remote display for a caller 10) Realizes wireless access by Wireless Conversion Pool