"13. Power Indicator Light
The power indicator will light when the amplifier is switched on.
14. Standby
This switch enables the operation of the power amp stage and speaker output.
Always turn this on at least 30 seconds after the Power switch (15). For silent
recording or practise this switch should be put in the standby position. This will
disable the power stage, but the emulated output will continue to work.
15. Power
This switch is used to turn the amplifier on and off. You should always turn this
switch on before turning on the Standby switch (14)."
Note--- There is a miss-spelling of practice. Not my bad!
Here is the link to the HANDBOOK
http://www.blackstaramps.com/pdf/handbooks/ht-5r-handbook.pdf
I hope this can get your head wrap around the solution. I know it help me.