Allied Telesis AT-S63 - Manual (Page 704)

Chapter 40: TACACS+ and RADIUS Commands
704 Section IX: Management Security
The following command selects RADIUS as the authentication protocol
with a global encryption key of leopard09 and a timeout of 15 seconds:
set authentication method=radius secret=leopard09 timeout=15
The following command removes the current global secret from the
RADIUS client without assigning a new value:
set authentication method=radius secret=none