Project: AlarmClock

Usage instructions for the alarm clock


The AlarmClock uses a DCF77 receiver module to get the current official German standard time from a wireless transmitter located near Frankfurt, Germany.

Synchronization takes place on every 58th minute in the hour. If after five minutes of trying no correct time signal has been received or decoded, an error counter is increased and the receiver is turned off until the next hour. The display shows rcv in the top line when the DCF77 signal reception is active. Between successful synchronizations and when the clock is powered off, a high-precision, battery buffered real time clock chip takes care of timekeeping.

Two alarm modes can be used: The first one, called absolute alarm mode, lets the user set a specific time (e.g. "at seven in the morning"). When this time has come, and the clock is powered on, the alarm goes off. This alarm mode is marked with an at @ symbol before the alarm time, if this is displayed.

Using the second mode, called relative alarm mode, the user can set a time duration, like "seven hours from now". "Now" here means the moment the alarm is activated. Using this mode, a user can program the clock to let him sleep for a defined amount of time, given that the alarm is turned on when going to bed. In this mode, the alarm time is marked with a plus (+) sign.

Once the alarm rings, the user can decide either to turn it off by dialing the number given in the clock's display, or shortly lift and place back the handpiece to activate snooze mode. In this mode, the alarm will be turned off, and start ringing again after five minutes. After a configurable number of snooze actions, though, the snooze function will be deactivated and the alarm will sound until it is turned off through the respective menu function.


Clock display

When turned on and in normal operations, the clock displays in the four display lines the following things.

  1. The current time and the number of hours the clock tried to synchronize with the DCF77 signal but failed. Usually, a 00 should be displayed there. When the DCF77 receiver is active, the string rcv is displayed in front of the sync error counter.
  2. If an alarm is activated, alarm settings are displayed in the second line.
  3. The current day of week, and date.
  4. A menu for setting alarm parameters and general configuration as explained further below.

When the clock display is active, as well as in any other screen mode, the display backlight can be turned on by lifting the telephone handpiece. Backlight will then turn on for up to about six seconds after the handpiece has been placed down again, and turn off then. When the alarm is ringing, the backlight is automatically switched on until the alarm is turned off.

All further instructions assume that the clock display is currently being shown. If any other display is activated, the user should follow the instructions given in the respective documentation section to get back to the clock display. Dialing 1 always brings the user one menu level upwards.

Configuring the alarm

Dialing 1 from the time display opens the alarm configuration menu.

To enter a new alarm time, the user can now choose between absolute and relative alarm mode. Dialing 4 activates relative alarm (marked Delta on the display), dialing 5 (marked AbsTime) lets the user enter an absolute alarm time.

After dialing 2 (Adjust), a new alarm time can be entered by dialing it in the format HH:MM, as displayed.

When either the alarm mode has been changed or a new alarm time was entered, the alarm is automatically turned off if it was on. It can be manually toggled on and off again by dialing 3 (On/Off) in the alarm configuration menu. In relative alarm mode, the timer starts to run when the alarm is switched on, and is reset when the alarm is switched off. The remaining time until the alarm rings is displayed in the second display line.

The alarm clock remembers the last alarm settings for both relative and absolute alarm mode, and remembers them separately for weekdays and weekend mornings: when an alarm is set on Sunday to Thursday, it is stored in the "weekday" memory, on Friday and Saturday, alarm settings are written to the "weekend" storage.

Dialing 1 returns to the time display.

Other settings

When dialing 5 from the time display, the configuration menu is opened. Here, the following options can be configured by dialing the respective number:


Last page update: 2007-07-24