【电学】DC电信技术（直流电信技术）

super-telephone telegraphy【通信】

direct-current telegraphy

dot-and-dash code telegraphy reception

order, fire or police TELEGRAPHY

acoustical telegraphy【通信】;audio frequency telegraph【通信】;

speed conversion dc telegraphy (direct-current telegraphy)

direct-current telegraphy, compensating variations

earth telegraphy