SECTION 5 1 8-41 1 - 1 00
TABLE B
CALL PROGRESS TONES
TONE
SIGNAL HEARD
REMARKS
Intercom Dial
128 Hz continuous
Time (IDT)
Intercom
256 Hz interrupted;
If any station is equipped
Audible
1 second on, 3
with a 2A HF AI unit, IAR
Ringback (IAR)
seconds off
consists of a single spurt
(1 second) of 128 Hz time
Intercom Busy
128 Hz interrupted
Tone (IBT)
at
1/2-sec intervals
256/512 Hz alternating
Tone heard when errors
Error
at 1/2-sec intervals
are made in setting up
Tone (GT)
dial-activated features.
Indicates procedure must
be restarted.
128 Hz for 250 ms
Tone heard when feature
Acknowledgment
has been properly activated
Tone (AT)
or canceled. Also heard on
paging access calls.
128 Hz interrupted at
Tone heard at start of all
75 ms intervals for
calls, followed by dial tone at
Reminder
1-1/4 seconds; then
stations that have activated
Tone (RT)
continuous 128 Hz
CFWD, ACBK or DND as a
reminder that feature is in
effect.
128 Hz for 500 ms
Tone heard by both parties
Override
of a conversation when a
Tone (OT)
station exercising OVERRIDE
is bridged on line
Four bursts of 128 Hz
Tone heard when switchhook
Hold Tone
tone.
(HT)
A.
484A KTU-Station Interface Circuit
2 . 1 4
The
484A
KTUs are installed in j acks
6
through
18,
depending on the station codes
being installed. Each KTU contains the circuitry
for four station codes.
The
484A
controls the
station visual and audible signals from signals
received over the H,
BL,
and
A
leads, and also
Page 4
is flashed during a call. Hold
tone is always followed by
steady dial tone.
controls the station busy
and
.station hold features.
Control of the seized intercom link is also through
the station circuit.
Note:
Power interruptions greater than 1.7
seconds will release any calls in progress.
Stations that are off-hook when the power is
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