Radio Shack Chronomatic-280 User Manual page 5

For a playing time of 59 minutes or less, follow these steps.
1. While holding down SLEEP, repeatedly press MINUTE until the display
shows the desired minute setting.
2. Release SLEEP.
For a playing time of 1 hour or more, follow these steps.
1. While holding down SLEEP, press HOUR. The display shows 1:59.
2. Continue to hold down SLEEP and repeatedly press MINUTE until the
display shows the desired minutes setting.
3. Release SLEEP.
To turn off the radio before the programmed sleep time has elapsed,
press SNOOZE.