Ä COMP.DCOM.TELCOM ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ From : Mark J. Cuccia 26 Jul 97 17:06:34 Subj : MF-KP vs. DTMF (was Telephone / Gilligan) ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Leonid A. Broukhis wrote: > Mark J. Cuccia writes: >> As for signaling the called number, most inter-office trunks don't >> use dialpulses. And international or overseas trunks most certainly >> don't use dialpulse. Most likely, there was SF 2400/2600-Hz >> supervisory tones, and CCITT #5 address signaling, which was an >> extension of existing Bell-System 'domestic' signaling, using all >> fifteen possible MF tone-pair combinations. > Aren't there 16 MF tone-pair combinations? 0-9, #, *, A-D? > DTW, I had a modem that would produce A-D tones (as in ATDTABCD), but > the they were ignored by the telco. There are indeed sixteen DT-MF (Dual-Tone Multi-Frequency) pairs: 1 2 3 A (697 Hz) 4 5 6 B (770 Hz) 7 8 9 C (852 Hz) * 0 # D (941 Hz) Column-1 (1,4,7,*) is 1209 Hz Column-2 (2,5,8,0) is 1336 Hz Column-3 (3,6,9,#) is 1477 Hz Column-4 (A,B,C,D) is 1633 Hz But that is 'touchtone', a 4x4 arrangement of four 'high' frequncies (columns) and four 'low' frequencies (rows). A 'digit' is a pair of one of the 'low' and one of the 'high'. Touchtone/DTMF is sometimes used on interoffice trunks, but mostly is for customer loop signaling, and customer-produced 'end-to-end' signaling, such as entering your calling-card number, credit-card number, etc. ad-nauseum. In the original article, what I was referring to by "MF" was "Multi-frequency Keypulsing", which was developed by the Bell System as early as 1939 or 1940 (one of the first locations for its use was between #1XB offices in Baltimore), and eventually used for most all interoffice/toll signaling in the later 1950's all the way through the 1980's. There are six distinct frequencies (700 Hz, 900 Hz, 1100 Hz, 1300 Hz, 1500 Hz, 1700 Hz) for MF. Each tone-pair is two of these six frequencies in combination, and you get fifteen tone-pair possibilites. For most NANP/DDD/Bell-System 'domestic' toll addressing applications, only '1' thru '9', '0', 'Kp', and 'St' were used. But on international/overseas trunks (CCITT #5), there was also 'Kp-1' (which was NANP/DDD 'Kp'), 'Kp-2', 'Code-11', and 'Code-12', in addition to the twelve NANP/DDD domestic MF-tones. In the later 1970's, some of the other frequency pairs used on CCITT #5 were also used domestically, for various TSPS signaling applications. One of the earliest (1948) experimental pushbutton tone-dialing phones is pictured in Bell's magazines and the book "History of Engineering & Science in the Bell System, Switching Technology, 1925-75" (authored by Amos E. Joel, Jr, of Bell Labs). There was an experiment with such pushbutton tone-dialing in Pennsylvania (the town of "Media", IIRC), at an early #5XB central office. The phones were standard WECO model 302 phones, but instead of a rotary dial, there were two horizontal rows of buttons. The first row was numbered '1' thru '5', from left to right, and the second row was numbered '6' thru '9', '0', from left to right. The interesting thing about this phone was that "MF-KP" frequncies were used (numerical digits only - there was no 'Kp' nor 'St'), and _NOT_ the frequencies of "Touchtone" (DTMF) which was being developed in the late 1950's and early 1960's. Also, the frequencies were produced by 'plucking metal reeds', and not electronically. While the transistor was just being invented at that time (by Bell Labs), _vacuum-tubes_ were still the order of the day for electronics. And having residential and commercial telephone dialsets using vacuum tubes and external continuous power (to heat the tubes) was considered too costly and cumbersome! Of course, people had been using radios, phonograph players, etc. (and soon televisions) home-entertainment devices with tube amplifiers for years, but Bell didn't seem to want vacuum-tubes in telephones used by the general public, thus the 'plucked reed' method of tone-generation! Widespread use of MF-KP was being replaced with CCIS#6 beginning in the mid-1970's, and by SS7 in the late-1980's and onward. CCIS#6 and SS7 are 'out-of-voiceband' signaling, while MF-KP was in the voicepath (similar to touchtone/DTMF). MARK_J._CUCCIA__PHONE/WRITE/WIRE/CABLE:__HOME:__(USA)__Tel:_CHestnut-1-2497 WORK:__mcuccia@mailhost.tcs.tulane.edu|4710-Wright-Road|__(+1-504-241-2497) Tel:UNiversity-5-5954(+1-504-865-5954)|New-Orleans-28__|fwds-on-no-answr-to Fax:UNiversity-5-5917(+1-504-865-5917)|Louisiana(70128)|cellular/voicemail- --- ifmail v.2.10-tx8.3.lwz * Origin: TELECOM Digest (1:340/13@fidonet)