... /50HZ-DC12V/1A 3)Specifications:270*150*50mm 4)With pager quantity :180pcs An extemal power amplifier and the serial port ... ation.Freely set up the length of receiving music.Each pager can set different chord music.Number display types can be ... display of number:3pcsWith pager quantity : 180pcs Letters show: A,B,C,D,E,F,H,P(80 in English) Wireless Calling System