PP40是一种应用最广泛的CENTRONICS系列接口的打印机.它有8根数据线,1根地线,3根应答线.应答线中,一根为(?)线,此线出现了负脉冲即启动打印机接收数据并开始打印.这是计算机通知打印机接收数据并打印的信号.一根为BUSY线,它为高电平,表示打印机处于忙状态,这是打印机给出的拒绝计算机送数的信号.另一根为(?)线,线上出现的负脉冲,是打印机通知计算机已完成前一字符的打印,可以接收下一个字符数据的信号. The PP40 is one of the most widely used CENTRONICS series printers with eight data lines, one ground line, and three response lines. One of the answer lines is a (?) Line, and a negative pulse Start the printer to receive data and start printing.This is the computer to inform the printer to receive data and print the signal.A for the BUSY line, it is high, said the printer is busy, which is given by the printer refused to send the computer signal The other is the (?) Line, the negative pulse that appears on the line is the signal that the printer notifies the computer that the previous character has completed printing and can receive the next character data.