Wireless receiving heartbeat signal transmitted from heartbeat brooch chest band frequency is AM5.3HKz; Time display: hour minute second; Alarm clock function; Give alarm when heart rate exceeds the upper and lower limit values (60-220); Timing (maximum time-keeping is 23 hours 59 minutes 59 seconds 99); 12/24 hour displaying format; EL back light; Keystroke tone; 3ATM water resistant. Specification: Case material: plastic Watchband material: rubber Case diameter: about 5cm Watchband width: about 2.1cm The heart rate chest belt and watch have a maximum transmission range of about 100 centimeters