Push-button telephone
Western Electric experimented as early as 1941 with methods of using mechanically activated reeds to produce two tones for each of the ten digits and by the late 1940s such technology was field-tested in a No.
[4] On 18 November 1963, after approximately three years of customer testing, the Bell System in the United States officially introduced dual-tone multi-frequency (DTMF) technology in Carnegie, Pennsylvania and increased its use in Greensburg, under its registered trademark Touch-Tone.
[5] Over the next few decades touch-tone service replaced traditional pulse dialing technology and it eventually became a world-wide standard for telecommunication signaling.
The concept of push buttons in telephony originated around 1887 with a device called the micro-telephone push-button, but it was not an automatic dialing system as understood later.
[7] After initial customer trials in Connecticut and Illinois, approximately one fourth of the central office in Findlay, Ohio, was equipped in 1960 with touch-tone digit registers for the first commercial deployment of push-button dialing, starting on 1 November 1960.
[12] The use of tones instead of dial pulses relied heavily on technology already developed for the long line network, although the 1963 touch-tone deployment adopted a different frequency set for its dual-tone multi-frequency signaling.
[17][18] Between 1971 and 1973, Bell Laboratories in the United States combined MOS technology with touch-tone technology to develop a push-button MOS touch-tone phone called the "Touch-O-Matic" telephone, which could store up to 32 phone numbers in an electronic telephone directory stored on memory chips.
This was made possible by the low cost, low power requirements, small size and high reliability of MOS transistors, over 15,000 of which were contained on ten IC chips, including one chip for logic functions (such as shift registers and counters), one for the keypad dial interface, and eight for memory storage.
][15] or charge their few remaining pulse-dial users the higher tone-dial monthly rate[22] as rotary telephones become increasingly rare.
[citation needed] While a tone-to-pulse converter could be deployed to any existing mechanical office line using 1970s technology, its speed would be limited to pulse dialing rates.
[citation needed] The DTMF keyboard layout broke with the tradition established in cash registers (and later adopted in calculators and computers) of having the lower numbers at the bottom.
This led to the addition of the number sign (#, pound or diamond in this context, hash, square or gate in the UK, and octothorpe by the original engineers) and asterisk or star (*) keys in 1969.
[citation needed] Later, the hash and asterisk keys were used in vertical service codes, such as *67 to suppress caller ID in the Bell System.
[citation needed] As telephone companies continued to levy surcharges for touch-tone service long after any technical justification ceased to exist,[34] a push-button telephone with pulse dialing capability represented a means for a user to obtain the convenience of push-button dialing without incurring the touch-tone surcharge.
[citation needed] In the 1950s, the Dutch electronics concern Philips developed a direct current (DC) signaling method for dialing telephone numbers, for use in the UB-49 private branch exchange (PBX) system.
[38] Most analog telephone adapters for Internet-based telecommunications (VoIP) recognize and translate DTMF tones but ignore dial pulses, an issue which also exists for some PBX systems.
