TP-Link T1600G-18TS Configuration Manual page 626

Configuring Network Security AAA Configuration
On TACACS+ server, configure the value of "enable 15" as the Enable password in the
configuration file. All the users trying to get administrative privileges share this Enable
password.
The logged-in guests can get administrative privileges by using the command
Tips:
enable-admin and providing the Enable password.
Configuration Guide 603