... ,Lock card, lock terminal.6,Send polarity reversal signal for billing meter while connection.7,Sending 12/16KHz pulse for billing meter while ... hour when out of mains supply. (Optional)10,Transmit tariff for our company phone billing meter. (Optional)Technical Specifications1,Work frequency ... sensitivity: 99.99%9,Insertion loss: ≤0.5dB 4 line GSM Fixed Wireless Terminal/FWT