a manual stop clock. A stop clock, also known as a stopwatch, is a handheld timepiece designed to measure the duration between its activation and deactivation. Here are some key aspects:

1. Basic Operation:

   • The stop clock is started and stopped manually by pressing a button.
   • It provides precise timing for various activities or events.

2. Adjustable Calibration:

   • The stop clock allows you to adjust its calibration based on your preferences, such as paper type, processing method, and enlarger characteristics.
   • This feature is especially useful when determining burn-in times during photographic printing.

3. Exposure Timing:

   • In photography, the stop clock assists with exposure timing.
   • It helps photographers control the duration of light exposure during the printing process.

4. Focusing and Manual Exposure:

   • Use the stop clock to time the exposure accurately while focusing and manually adjusting the enlarger settings.
   • This ensures precise results in the darkroom.

5. Test Strips and Printing Sequences:

   • Create test strips to determine the optimal exposure time for a specific print.
   • Perform complex printing sequences, including burning-in specific areas.

6. Other Features:

   • Clear and edit programs.
   • Change channels for multiple burn-in exposures.
   • Abort exposures or sequences.
   • Dodge specific areas during printing.
   • Handle errors gracefully.

7. Installation and Safety:

   • Ensure proper installation, including connecting the stop clock to your enlarger and safelight.
   • Follow safety precautions, including proper grounding and electrical safety.