Panasonic KX-HTS Series Setup Reference Manual page 10

 SIP Trunk Property continued – SIP Carrier-1
[Calling Party]
1. Header Type:
2. Host Name:
3. Format:
4. Send CLIP of caller when call from SIP
Carrier is forwarded to same SIP carrier:
[Called Party]
5. Format:
Leave From Header
Not required
Leave Without "+"
Leave Enable
Leave Without "+"
10