Re:4 more DTMF Tones (Score 1)

While it is true that there are actually 16 DTMF tones from the original ATT spec, but column #4 (A,B,C, and D) is rarely offered or accessible from 99% of the dialer IC's which are in current existance in standard CPE. Your statement that "EVERY tone generating device is capable of generating these 4 additional tones" is absolutely false. The TYPICAL dialer IC never utilizes the 4 extra tones for cost and practical reasons, it would require 4 additional IC pins (one for each row connected to the 4th column). Typical you have to use an expensive "niche" IC chips like Teletone makes which have combo DTMF generators and recievers to get the additional DTMF tones. Most corded phones use a dedicated dialer IC (again 99% without A,B,C,and D) but all modern cordless phones use embedded software for tone dialing and the DTMF frequencies are the conventional 12 digits commonly used. As such, all phones not having the extended digits A,B,C, and D would be obsoleted by using this method, which is unacceptable. Further to this point DTMF "A" and DTMF "D" are now being used in the phone networks as the ACK tone on Type 2 and 3 CID. Type 2 (Call Waiting ID) uses the "D" as the ack and Type 3 (ADSI)uses DTMF "A" as the ACK signal, with this in mind the FCC and the Telcos would never go for the extended DTMF tones to be used in standard dialing. Like it or not, additional numbers added to what we dial now is inevitable. With the explosion of cell phones, fax machines, and people getting cheap additional lines for internet and "teenager" lines, there is simply no alternative. The FCC opened many previously unavailable area code numbers up a few years ago and now they are all basically used up. Other countries like Hong Kong and Taiwan "bit the bullet" and added 1 more digit to all calls dialed several years ago and they don't have too much trouble communicating by phone.