From 1850 to the mid 20th century industrial countries used the electric telegraph as a long distance person-to-person text message service. A telegraph system consisted of two or more geographically separated stations linked by wire supported on telegraph poles. A message was sent by an operator in one station tapping on a telegraph key, which sent pulses of current from a battery or generator down the wire to the receiving station, spelling out the text message in Morse code. At the receiving station the current would activate a telegraph sounder which would produce a series of audible clicks, and a receiving operator who knew Morse code would translate the clicks to text and write down the message. By the 1870s, most industrial nations had nationwide telegraph networks with telegraph offices in most towns, allowing citizens to send a message called a "telegram" for a fee to any person in the country. Submarine telegraph cables allowed intercontinental messages called "cablegrams".