1 General
2
Electrical levels for tones
3
Acoustical levels for tones
4
Dial tone
5
Ringing tone
6
Busy tone and congestion tone
7
Special information tone
8
Warning tone to indicate that a
conversation is being recorded
9
Payphone recognition tone
9.3 Duration and level
10 Call waiting tone
11 Caller waiting tone
12 Machine recognition of tones
Annex A Digital generation of tones
Annex B Examples for limitation of
spurious components of the dial tone with respect to interference with the
frequencies recommended for pushbutton telephone sets in Recommendation Q.23
B.1 Method A (used by ATT)
B.2 Method B (used by the Federal Republic of Germany)