DTMF is not a sequence. It's a pair of frequencies sent down the line. One frequency is selected from the row the key is in and the other from the column on a standard dial layout:1 2 3 A 697Hz 4 5 6 B 770Hz 7 8 9 C 852Hz * 0 # D 941Hz 1209 1336 1477 1633 Hz Hz Hz Hz
Most phones do not have the ABCD column. On military phones it may be labelled Flash Override, Flash, Immediate, and Priority. Some modems let you dial A, B, C, or D. These codes are sometimes used for controlling ham radio gateways to landline phones.
What do you dial for an international call? It's a sequence of digits, each transmitted as a pair of frequencies. From the USA, this is often 011 followed by the country code followed by the number.
Caller-ID is not transmitted by DTMF. It is sent by modulation of the same type used by a Bell 202 modem.
Gordon L. Burditt