Nortel DMS-250 - Termination to a PTS Trunk; Audio Tone Detectors

Call control procedures 5-15
Digital Switching Systems DMS-250 ISDN Reference Manual MWC14 (CSP14)
Termination to a PTS trunk
Figure 5-7 shows termination to a PTS trunk, a PRI call that requires
in-band DTMF digit collection. The PBX ensures that the subscriber is
capable of providing DTMF digits.
Figure 5-7
Digit collection PRI-to-trunk
Originating
user
Network
Terminating
PTS trunk
SETUP (CR,CID, BC, NSF,CDN,CGN,
DIE, OCN, RGN)
CALL PROC
(Translations and routing complete)
Trunk returns answer supervision
CONN
(Billing starts)
CONN ACK
IN-BAND DIGITS (DTMF)
PROG
(PI = call not end-to-end ISDN)
when called party answers.
Call terminates to trunk.
Note: Dashed lines indicate optional messages.
Audio tone detectors
Audio tone detectors (ATD) provide a means for the DMS-250 switch to
detect an answer on a circuit that does not support supervisory signals for
hardware answer. Audio signals generated from the called party determine
when the called party has answered.