Timex Digital Chest Transmitter  T54051

Digital Heart Rate Sensor features

• Digital FM transmission for clear signals around exercise equipment and power lines
• Synchronized transmission prevents cross talk from other HR  monitors
• Smart transmission for long battery life
• On-the-chest monitor provides continuous HR readings during even the most intense activities
• Comfortable, adjustable elastic strap.
• Replaceable batteries
• 2 year battery life**
• Sensor–Water resistant 30m (Sensor will not provide accurate heart rates when underwater.)