... chord music 2)Power supply: Ac220V/50HZ-DC12V/1A 3)Specifications:270*150*50mm 4)With pager quantity :180pcs ... An extemal power amplifier and the serial port communic ation.Freely set up the length of receiving music.Each ... automatically deleted after the set time ending, in meanwhile, and call time infinite can be selected, choosing to manually ... ,D,E,F,H,P(80 in English) Wireless Calling System