Telegrams have become one of the easiest handouts to produce for period Call of Cthulhu games. Multiple blank forms are available, including the three posted here on Propnomicon (One, Two, Three).
You can add more verisimilitude to the experience by using one of the numerous telegraphic codes. These were handy phrasebooks that allowed users to shorten their messages, saving money. They could also serve as simple ciphers for encoded messages, with senders and receivers coordinating ahead of time which telegram code book they would use for correspondence.
The Adams Cable Codex is a great example of the genre. Click through the link and you can view and download a complete copy from archive.org. In addition to the hundreds of code phrases you'll find some interesting suggestions for how to use multiple cable addresses and third party cutouts (!) for more secure communications.
You might want to have a look at Evans basic English code, which is less verbose, useful and even readable:
ReplyDeletehttps://people.duke.edu/~ng46/collections/evans-basic-english-1947.pdf