08208605 is referenced by 3 patents and cites 684 patents.

An emergency services key (e.g., ESQK or ESRK) is guaranteed to be available from a limited size ESQK pool. A plurality of ESQKs are grouped into a pool of emergency service keys “ESQK Pool ID”, each including anywhere from 1 to N number of ESQKs. Each ESQK preferably has a “Timestamp”, information relating to the specific emergency E911 call (“Call Data ID”), a guard timer, and an optional hold timer. The ESQK having a Call Data ID=“NULL”, and having the oldest Timestamp, is chosen for selection. If no such ESQK has both Call Data ID=NULL and the oldest Timestamp is found, then the ESQK with merely the oldest Timestamp is selected. The timestamp is reset to a current time plus a guard timer, or hold timer if desired.

Title
Extended efficient usage of emergency services keys
Application Number
11/987048
Publication Number
8208605 (B2)
Application Date
November 27, 2007
Publication Date
June 26, 2012
Inventor
Victor Burton
Bellevue
WA, US
John Gordon Hines
Kirkland
WA, US
Yinjun Zhu
Kirkland
WA, US
Gerhard Geldenbott
Seattle
WA, US
Agent
William H Bollman
Assignee
TeleCommunication Systems
MD, US
IPC
H04M 11/04
View Original Source