Aastra Telecom 53I - Manual (Page 54)

Sylantro Interoperability Features
48 RN-001029-00, Rev 03, Release 2.1
IP Phone Release Notes 2.1
To use this format with the default dial plan terminator (#), the # sign
required by Sylantro as a delimiter should be represented as an escaped
character by using the sequence %23. The speed dial format for an
external number that includes an optional billing code becomes:
*50<billing code>%23<phone number>
Numbers Not Requiring Billing Codes
Billing codes are not required for the following two types of calls:
• Emergency calls (E911)
• Calls between extensions