[plapsley]

Yes. See https://en.wikipedia.org/wiki/Signaling_System_No._5

SS5 was derived from AT&T's US MF signaling system, described in "Signaling Systems for Control of Telephone Switching" by Breen and Dahlbom, Bell System Technical Journal, November 1960. PDF here: https://explodingthephone.com/hoppdocs/breen1960.pdf

The BSTJ article has a discussion on international signaling on pp. 1430-1441.

[plapsley]

CCITT (ITU-T) version can be downloaded for free (!) from their website. https://www.itu.int/rec/T-REC-Q.140-Q.180-198811-I/en Specific download link in English is https://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-Q.14...

[jasomill]

Fascinating article. See also

https://web.archive.org/web/20120314023131if_/http://www.alc...

for an early technical article describing the implementation details of the familiar DTMF "touch tone" dialing system, noting that the precise details differ from the final implementation — in particular, the high group frequencies increased from 1,094/1,209/1,336/1,477 Hz to 1,209/1,336/1,477/1,633 Hz, possibly to mitigate the "pulling" effect described on pp. 251–252 (though I can find no reference for the rationale).