CID
Calling identity delivery (CID) enables called terminals to display the calling identity information, including the calling number, calling name, date, and time.
With the CID function, calling numbers and calling time in single-data-message format are transmitted or received in an on-hook state. When the CID function is combined with services such as call forwarding—unconditional (CFU) and call forwarding—busy (CFB), calling identity information can also be transmitted if required. A message in the single-data-message format contains the following information:
Date and time when the voice call occurs (MM DD hh:mm)
Calling number if CID is enabled on the device
P if CID is disabled on the device
O if the terminating PBX fails to obtain the calling number (for example, the originating PBX end does not send it)
A message in the multiple-data-message format contains the following information:
Date and time when the voice call occurs (MM DD hh:mm)
Calling number and calling name if CID is enabled on the device
Two Ps for the calling number and the calling name if CID is disabled on the device
O if the terminating PBX fails to obtain the calling number (for example, the originating PBX end does not send it)
O if the terminating PBX fails to obtain the calling name (for example, the originating PBX end does not send it)
The FXS voice subscriber line sends the calling identity information to the called telephone. The calling identity information is sent to the called telephone through frequency shift keying (FSK) modulation between first and second rings. Therefore, the called user must pick up the telephone after the second ring to make sure that the calling identity information is sent and received correctly. Otherwise, the calling identity information might fail to be displayed.