Nortel DMS-100 Series Maintenance Manual page 128

3-12 SMS signaling
With a UTR, the SMS goes through the following steps:
1 Request a UTR channel.
2 Instruct the UTR to start monitoring tones.
3 When monitoring starts, the system informs the SMS of collected digits.
4 When the receiver is no longer required, the SMS frees the allocated
Note: The system requires a receiver request to start the sequence.
The SMS creates alerting tones to support the Deluxe Spontaneous Call
Waiting Identification (DSCWID) feature. A line with the DSCWID option
can establish a call and have a second call attempt to terminate that line.
When this event occurs, the SMS alerts the system. The types of signals that
alert the system are Subscriber Alerting Signal (SAS) or an SAS followed
by a Customer Premises Equipment (CPE) Alerting Signal (CAS). The
tones alert the DSCWID subscriber of the pending call, and the DSCWID
CPE of pending caller data.
The SAS is the tone that the subscriber recognizes as the "Call Waiting
Tone". The CAS alerts the CPE of forthcoming data. The system requires
SAS followed by a CAS to trigger an Analog Display Services Interface
(ADSI) compatible CPE to display the DSCWID options. The CAS tone
prepares the CPE to receive Caller Identification (CID) data.
The DSCWID CPE generates an acknowledge (ACK) tone to indicate
readiness to receive DSCWID data. If the CPE is ADSI compatible, the
CPE sends a DTMF A ACK signal in response to the CAS. When the CPE
is a SCWID CPE, the CPE sends a DTMF D ACK signal in response to the
CAS. When the system sends an alerting tone, the subscriber can control
disposition to the incoming call. The subscriber uses the following keys to
control the disposition:
A T-tone timer sets the maximum acceptable time between sending a flash
and the DTMF digit on an ADSI set. The SMS receives a flash signal from
the ADSI compatible CPE of the customer. The SMS starts a T-tone timer.
The value of T-tone is 600 ms. The system mutes the speech path during the
T–tone timer. The system uses the T-tone timer for the initial option of a
DSCWID call, and the CPE type does not affect this event. Any subsequent
DSCWID options on an ADSI set also use the T-tone timer.
297-8231-550 Standard 09.01 August 1998
The SMS normally performs some translations functions on the digits.
UTR channel.
CPE softkeys when the CPE is ADSI
hard-coded keys when the CPE is a SCWID
hard-coded keys when the CPE is a 2500 set