1878年英國(guo)人泰亞(ya)發明了電(dian)(dian)氣路牌機,后來又有了電(dian)(dian)氣路簽(qian)機。使用電(dian)(dian)氣路簽(qian)(牌)閉(bi)塞時,乙(yi)站同意(yi)甲(jia)站開(kai)(kai)車,乙(yi)站值(zhi)班員須向(xiang)甲(jia)站送電(dian)(dian),甲(jia)站才能從路簽(qian)(牌)機中取出一個銅質(zhi)圓棒(bang)形的路簽(qian)或銅質(zhi)圓餅形的路牌。司機在拿到(dao)路簽(qian)(牌)后,方準開(kai)(kai)車進入區間(jian),此時區間(jian)呈封閉(bi)狀態。