... ,Lock card, lock terminal.6,Send polarity reversal signal for billing meter while connection.7,Sending 12/16KHz pulse ... connection is also compatible.8,Support GPRS . (Optional)9,Rechargeable battery, keep conversation for at least 3 hour when out of mains supply ... . (Optional)10,Transmit tariff for our company phone billing meter. (Optional) Technical Specifications1,Work ...