Using the phone is second nature to most of us moderns so it’s easy to forget that not so long ago the telephone was not such a familiar object. By 1917, telephones were commonplace in offices and many homes, but as this Chesapeake and Potomac Telephony Company guide shows, phone etiquette still had to be spelt out:
“If you finish a telephone conversation and hang up your receiver without saying ‘Good-bye’ or something else to indicate that your part of the conversation is finished, the party with whom you are talking may remain at the telephone, wasting his time and keeping the line from being used by others. Perhaps he blames the operator for what he thinks is a cutting off of the conversation.”
Via Retronaut where you’ll find much more 1917 telephone advice.