==Phrack Inc.==
           Volume One, Issue Three, Phile 3 of 10

Signalling Systems Around the World

For those of you who have the desire to make international calls, this info may be of interest. Thanks to TAP and Nick Haflinger.

An old international system, now deceased. Used a 500 Hz tone interrupted at 20 Hz (Ring) for 1-way line signals.
Proposed "International Standard" that never caught on much. Used 600 Hz interrupted by 750 Hz. Still used in Australia, New Zealand and South Africa.
An early in-band system that uses 2280 for both line and register (!!). Used in France, Austria, Poland and Hungary.
A variation of 3, but uses 2040 and 2400 for end to end Tx of line and register. Used for international Traffic in Europe, but cannot be used with TASI (AKA Multiplex or "that dammed clipping").
This is the most popular, and the one used in the US. 2400 and the infamous 2600 are used for link to link (not merely end to end line signals. Registers are handled via DTMF (Touchtones). Anyone know what 2400 does??
CCITT 5 bis.
Just like above, but a 1850 Hz tone is used for TASI locking and transmission of line signals.
The newest and worst for phreaks. It uses digital data sent out-of-band to control the connection. In other words, the connection is made and billing started BEFORE you can get control.
A regional system like 5, but doesn't use the mysterious 2400 and can't use the multiplexer.
Probably the interface to AUTOVON, as it uses 120 Hz spaced tones for DTMF instead of 200. Also 3825 Hz is the blow-off tone instead of 2600.

The "Extra" tones

1700 + 700  = Inward Operator
1700 + 900  = Delay operator, also, in TSPS,STP (a "Zero Plus"-
              call from a coin phone)
1700 + 1100 = KP1 (Start recognition of special tones)
1300 + 1700 = KP2 (End recognition of special tones)
12-85 Data Line. CIS 72767,3207: TWX 650-240-6356