GLOSSARY
On outgoing calls, System 25 transmits a request for service to the distant switching system by grounding the trunk ring lead. When the distant system is ready to receive the digits of the called number, that system grounds the trunk tip lead. When System 25 detects this ground, it removes the ground from the ring lead and the trunk is ready for service.
Home Numbering Plan Area (HNPA) Code
The local area code. Does not have to be dialed to place calls to numbers within the local numbering plan area.
After establishing a connection with the distant switching system for an outgoing call, the system waits a nominal 65 milliseconds before sending the digits of the called number. This allows time for the distant system to prepare to receive the digits. Similarly, on an incoming call, the system has 65 milliseconds to prepare to receive the digits.
I n t e r c e p t T o n e
On System 25, this tone is the same as Reorder Tone. Indicates a dialing error or denial of the service requested.
I n t e r f a c e
A common boundary between two systems or pieces of equipment.
Internal Call
A connection between two stations within the system. Sometimes called an inside or intercom call.
A red lamp on a multiline voice terminal that lights to show which call appearance will be selected when the handset is lifted or which call appearance is active when a user is
