... 3)Specifications:270*150*50mm 4)With pager quantity :180pcs Wireless call bell systemAn extemal power amplifier and the serial port ... extension, numbers can be from01-99, the letter from the A1-A9, etc. (the letter include ABCDEFHP).05 The display time ... ,B,C,D,E,F,H,P(80 in English) Wireless call bell system