HAM Radio 73 and 88

In 1859, Western Union standardized on the "92 code", a series of telegraphic abbreviations in which numbers (originally 1 to 92) were assigned meanings.^[6] These were later included as part of the "Philips Code", a series of abbreviations first published in 1879 by Walter Phillips of the Associated Press for use in the telegraphic transmission of press dispatches.^[7]
While most of the codes have fallen into disuse, the form 19 and 31 train orders remained in railroad use long beyond the end of landline telegraphy, the use of '30' at the end of a news wire story was continued through the teletypewriter era and the '73' and '88' greetings remain in use in amateur radiotelegraphy.

Western Union codes

Abbreviation	Meaning	Abbreviation	Meaning
1	Wait a minute.	25	Busy on another wire.
2	Very Important.	26	Put on ground wire.
3	What time is it?	27	Priority, very important.
4	Where shall I go ahead?	28	Do you get my writing?.
5	Have you business for me?	29	Private, deliver in sealed envelope.
6	I am ready.	30	No more - the end.
7	Are you ready?	31	Form 31 (permissive) train order.
8	Close your key, stop breaking.	32	I understand that I am to ....
9	Priority business. Wire Chief's call.	33	Answer is paid.
10	Keep this circuit closed.	34	Message for all officers.
12	Do you understand?	35	You may use my signal to answer this.
13	I understand.	37	Inform all interested.
14	What is the weather?	39	Important, with priority on through wire.
15	For you and others to copy.	44	Answer promptly by wire.
17	Lightning here.	55	Important.
18	What's the trouble?	73	Best Regards.
19	Form 19 (absolute) train order.	77	I have a message for you.
21	Stop for meal.	88	Love and kisses.
22	Wire test.	91	Superintendent's signal.
23	All stations copy.	92	Deliver Promptly.
24	Repeat this back.	134	Who is at the key?

Two non-standard codes, rarely-used, were coined within the amateur radiotelegraph service. The Young Ladies Radio League (YLRL) organized in 1939 and quickly coined '33' as "Love sealed with mutual respect and friendship between one YL and another YL".^[8] More recently, '72' has been used in QRP operation to signify a '73' sent with reduced transmitter power.