Silent At Office application is use for, if you want to set your device volume for particular office time.

with this app you just want to select your office start and end time, and after that you want to select ringer mode like "Ring", "Vibrate", "Silent".

After that just start the service, when ever your device current time is in between your office start and end time it's automatically set the ringer mode and volume as per you select earlier.

If you select ringer mode as a "Ring" it's given volume control option for set the volume.

Even you restart your device, This app service is also working.