Panasonic KX-TD500 System Reference Manual page 1209

46.00 Automatic Busy-out Count (ABC)
Description
It is administrable to busy out the invalid CO line automatically to prevent
extension users from accessing it by monitoring the loop current sent through
CO line.
(Password level: Three or higher)
One of the following three options is assignable on a CO line basis.
(1) N=000
On CO calls, the system monitors a loop current sent through the CO line,
and if a loop current is not detected, busy tone is sent to the caller.
(2) N=001 to 240
On CO calls, the system monitors a loop current sent through the CO line,
and if a loop current is not detected pre-assigned times (001 to 240)
consecutively, busy tone is sent to the caller.
Then the system busies out the corresponding CO line automatically.
(3) N=241
On CO calls, the system does not monitor the loop current sent through the
CO line, therefore, CO line is always seized by extension users whether
loop current is running or not.
Refer to Section 11-C-44.00 "WS 2" L-COT/G-COT Busy Out Looprelay.
Input Format
Mode
A B C
Index Number
Index Number
10101 to 31416
Item Number Input Values
Item
Assigning Items
Number
None
Automatic Busy-out Count
Index Number CR
xxx (000 to 241)
(Loop Current Detection)
000 :
001 to 240 :
241 :
(Default = 241)
11-C-83
Explanation
Physical Number of the Trunk Port
Input Value
Yes
Yes
if loop current is not
detected by the pre-
assigned times (001 to 240)
No
(Automatic Busy-out)
No
Yes
No