Nortel DMS-100 Series Maintenance Manual page 93

Signaling for RLCM-EDC 2-9
Call origination
Messaging transmits the on- and off-hook messages that allow the host XPM
to identify subscribers that require service.
When a subscriber lifts the handset from the cradle, a voltage source
provides a steady flow of current through the transmitter. The voltage
source is in the RLCM. The LCM processor detects this current and sends
an off-hook message to the central office (CO).
The CO recognizes the off-hook signal as a request for service. The CO
allocates a channel on a DS-1 link to serve the subscriber line. The CO
applies dial tone to the line.
The subscriber line transmits open pulses or dual tone multi-frequency
signals through the RLCM to the CO. The type of signals that the subscriber
line transmits depends on the type of telephone. The CO analyzes the digits
and determines the placement of an interoffice call. The calling end of the
trunk is seized. The CO transmits a connect signal forward to the called end
of the trunk. The connect signal is a sustained off-hook signal. This signal
indicates a request for service and continues until a break occurs in the
connection.
Tone generation
The NTMX76BA messaging circuit pack contains the same downloadable
tone circuits as the tones on the NT6X69LA/LB circuit packs. The DMS
core supplies the tone data according to system configuration information.
A static random access memory (SRAM) device on the NTMX76BA card
holds the tone data.
The NTMX76BA messaging circuit pack contains a set of tones for North
American networks use in a read-only memory (ROM) device. This tone set
is the same tone set implemented on some NT6X69 messaging packs. These
messaging packs include the NT6X69AC. These messaging packs can have
the tone ROM.
Hardware on the NTMX76BA messaging circuit pack transmits the tone
data into parallel speech bus timeslots. This transmission routes the tone
data to specified line cards and subscriber sets. The call processing software
defines the line cards and subscriber sets.
End-to-end signaling
End-to-end signaling allows a subscriber to send DTMF signals to the far
end. The subscriber uses the keypad of a Meridian Digital Centrex (MDC)
Meridian business set (MBS) to send the signals. If the subscriber presses
specified keys at the MBS, the subscriber can outpulse DTMF signals to the
machine. These DTMF signals start, stop, rewind, and playback the
DMS-100 Family Maintenance Manual ABSK007