AT&T MERLIN LEGEND System Reference Manual page 418

Features
Telephone Differences
Single-Line Telephones
Mode Differences
Considerations
The TTR is allocated for 15 seconds at the beginning of the call. Each time the
user presses another digit, the TTR timer is reset for another 15 seconds. If the
user does not dial a digit within the 15-Second time frame, the TTR is removed
from the call and, after about 24 seconds, the call is disconnected and the user
hears a recording or a fast busy.
The system is factory-set to generate touch-tone signals for all lines/trunks when
users dial outside calls. The factory setting can be changed for individual rotary
lines/trunks so that touch-tone signals are converted to rotary pulses for
transmission to the central office.
Touch-tone single-line telephone users cannot make calls by using lines/trunks
programmed for rotary operation. The touch-tone signals generated from the
telephone are transmitted to the central office at the same time the rotary-dial
signals are sent by the system. The central office receives both signals and
cannot process the call.
In the Hybrid/PBX mode, the factory setting for DID trunks is rotary dial. Since
DID trunks are used only for incoming calls, the setting need not be changed.
Tie trunks are set up either to send signals to or receive signals from another
PBX, or they are setup to be bi-directional—to send and receive signals. If
the system has bi-directional tie trunks, the signaling can be set for both
directions independently—for example, outgoing signaling can be rotary and
incoming can be touch-tone. The local telephone company should be
consulted for more information.
The audible feedback for touch-tones generated when a user presses a
dialpad button can be heard by any user who shares a Personal Line or a
Shared System Access button (Hybrid/PBX only) with the telephone that is
used to make a call. Therefore, when dialing confidential numbers such as
passwords or account information, the user should take precautions, such as
activating Privacy, to prevent others from hearing the touch-tones.
The touch-tone duration for multiline telephone touch-tone signals is 50 ms
and is not adjustable. If the user needs a longer duration when calling an
answering machine, dictation machine, or computer, it is recommended that
the user hold the dialpad button down longer.
Touch-Tone or Rotary Signaling 2-369