Panasonic KX-TDA15 Features Manual page 361

2.1 System Configuration—Hardware
Programming Manual References
PC Programming Manual
3.7.5 [1-1] Slot—Extension Port
3.10.17 [4-3] DSS Console—Flexible Button—Pair Extension
PT Programming Manual
[007] DSS Console Paired Telephone
[600] EXtra Device Port (XDP) Mode
Feature Guide 361