Panasonic KX-TD500 System Reference Manual page 1204

(5) Mode Selection of Calls Arriving at ATT
When two attendant consoles are connected to the system, one of the
following three types of Incoming Mode can be selected.
Options 2 and 3 work only for the incoming outside call routed via a CO line
which belongs to the Trunk Group whose Incoming Mode (Day) is assigned
as "ATT."
(Parameters)
1. Load Sharing
Incoming outside calls are distributed evenly to two attendant consoles
so that they can share the same load. (default)
2. Simultaneous Ringing
An incoming outside call rings at two attendant consoles simultaneously.
3. Interconsole IRNA
If an incoming outside call ringing at one attendant console is not
answered within a specified time period (Attendant Overflow Time), it will
be automatically transferred to another attendant console automatically.
(6) Centrex ARS Mode
Not available.
(7) Waiting for Second Dial Tone Mode
In some area, upon completion of facility access code entry, the extension
user must ensure the reception of the second dial tone from the Central
Office before continuing to dial the telephone number.
(Parameters)
Y : The system waits for the second CO dial tone.
N : The system does not wait for the second CO dial tone. (default)
(8) Polarity Reversal Mode
With an RCOT card (KX-T96183), the system determines the start and
completion of calls by detecting a reversal of CO line polarity.
In some areas, however, CO doesn't send a reverse signal when a certain
type of special telephone numbers is dialed.
In this case, select "1. Special Mode."
When "1. Special Mode" (default) is selected, the system connects a speech
path when "External Interdigit Timer" (5 s - default) expires, or when it
detects a reversal of CO line polarity.
(Parameters)
1. Special Mode (default)
The system connects a speech path when "External Interdigit Time-Out"
expires, or it detects a reversal of CO line polarity. Call duration time
counting starts when the system detects a reversal of CO line polarity.
2. Normal Mode
The system connects a speech path and starts counting the call duration
time when it detects a reversal of CO line polarity.
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