m-982-02 Clare, Inc., m-982-02 Datasheet - Page 4

• Manufacturer Part Number: m-982-02
• Description: Precise Call Progress Tone Detector
• Manufacturer: Clare, Inc.

M-982-02
Call Progress Tone Detection
Call progress tones are audible tones sent from
switching systems to calling parties to show the status
of calls. Calling parties can identify the success of a
call placed by what is heard after dialing. The type of
tone used and its timing vary from system to system,
and though intended for human ears these signals can
provide valuable information for automated calling sys-
tems.
The M-982-02 contains five signal detectors sensitive
to the frequencies often used for these progress tones.
Electronic equipment monitoring the DET n outputs of
the M-982-02 can determine the nature of signals
present by measuring their duty cycle. See the Tri-
State Timing Diagram on page 5 for a diagram of a cir-
cuit that could be used to permit a microcomputer to
directly monitor tones on the telephone line. Much of
the character of the progress tones is in their duty
cycle or cadence (sometimes referred to as interrup-
tion rate). This information, coupled with level and fre-
quency indication from the M-982-02, can be used to
decide what progress tones have been encountered.
For example,dial tones as shown in the Call Progress
Tone tabel on page 3 are usually “on” continuously and
4
Truth Table
Signal Present (fo)
350 Hz
400 Hz (Note)
620 Hz (Note)
440 Hz
480 Hz
425 Hz
Other (no detect)
Any
Any
Any
Any
Any
1/open
Mode
X
0
X
X
X
X
X
X
X
X
X
Det 1
1
X
X
X
X
X
0
0
0
Det 2
X
1
1
X
X
X
0
0
0
High Impedance
High Impedance
High Impedance
www.clare.com
Det 3
X
X
X
X
X
1
0
0
0
last until the first dial digit is received by the switching
system. Line Busy, on the other hand, is turned off and
on at a rate of 1 Hz with a a 50% duty cycle, or an inter-
ruption rate of 60 times per minute (60 IPM). The tones
can be distinguished in this way. It should be noted that
while such techniques will usually be effective, there
are some circumstances in which the M-982-02 cannot
be accurately used. Examples include situations
where ringback tone may be short or not even encoun-
tered. Ringback may be provided at ringing voltage fre-
quency (20 or 30 Hz) with some harmonics and may
not fall in the detect range, and speech or other strong
noise may obscure tones making cadence measure-
ment difficult.
Standards do exist and should be consulted for your
particular application. In North America AT&Ts “Notes
on the Network” or EIAs RS-464 PBX standard should
be reviewed. In Europe tone plans may vary with
locale, in which case the CEPT administration in each
country must be consulted. Outside these areas,
national PTT organizations can provide information on
the systems within their borders.
Det 4
X
X
X
X
1
X
0
0
0
Det 5
X
X
X
X
X
1
0
0
0
Strobe
1
1
1
1
1
1
0
0
0
X
0
X
PD
0
0
0
0
0
0
0
1
0
0
0
1
OE
1
1
1
1
1
1
1
1
1
0
0
0
EN
X
X
1
1
1
1
1
1
1
0
1
0
Rev. 4