18.3.1. Prerequisites 
System
The following prerequisites must be met before you can activate SPE
in a system:
- Depending on the certificate verification level and all (v)HG 3500 gateways in this system may be assigned SPE certificates and/ or at least one CA certificate (see Section 1.3.4, “Certificate Verification Level”).
- All NCUI2 boards must be replaced by NCUI2+ or NCUI4.
- All (v)NCUI boards must have Master Encryption Keys (MEKs) configured.
- All components must be synchronized via the NTP server.
IMPORTANT:
Do not use Assistant as an NTP server for IP phones,
as it is not supported. It has a limited number of buffers which makes
it unreliable in large deployments.