Panasonic KX-TD500 System Reference Manual page 1211

Index Number Input Values
Item
Assigning Items
Number
None
CO Access Instantly
Conditions
(External First Digit Time-Out timer assignment)
When CO Access Instantly is utilized, we recommend to set System-System
Timer "External First Digit Time-Out" timer longer than length of CO dial tone
delay.
This setting can be ranged from 5 to 120 seconds.
Refer to Section 10-D-3.00 "System Timer" or
Section 11-C-6.00 "System Timer (TIM)".
Input Value
Y : Enabled
N : Disabled
(Default = Y)
11-C-85