Slightly different to the T31c Transmitter, the slim, light and waterproof T31 doesn’t have the benefit of coding for interference free transmission. However, its purpose remains the same: to transmit your heart rate to your wrist unit ECG (electrocardiogram) accurately

How do I know what size I need?
The measurement for the transmitter should be taken right below the pectoral muscles, or breasts. If you are borderline between two sizes, go with the next size larger.
Polar Transmitter sizes are calculated in inches and should be based on personal comfort level. If you order the incorrect size, you can exchange just the elastic strap portion of the transmitter, or order a replacement located in the strap area of accessories.
What is I have a Pacemaker, will it interfere with a Polar Heart Rate Monitor?

A Pacemaker and the Polar Heart Rate Monitor

Persons who have a pacemaker or defibrillator use the Polar heart rate monitor at their own risk. Before starting use, we always recommend an exercise test under doctor’s supervision. The test is to ensure the safety and reliability of the simultaneous use of the pacemaker and the heart rate monitor.

The manufacturer of the defibrillator has to approve the simultaneous use of Polar Heart Rate Monitor and the defibrillator.

Technical information about radiated magnetic field of the transmitter:

Polar Non-Coded Transmitter:
Transmission frequency: 5kHz
Means of transmission: On/Off -modulation, magnetic field by means of a 5-7ms burst for each heart beat.
Polar Coded Transmitter:
Transmission frequency: 5kHz
Means of transmission: On/Off -modulation, magnetic field by means of a train of three 5ms bursts for each heart beat Time Interval Coding.

The strength of the magnetic field right next to the transmitter is 5 uT (micro tesla) and 1 nT at 1 m distance. Even in the worst case the radiated power is under 2 nW

Chest Strap Sizing:
“Med (25-54 Inches)”
“Large (33-63 Inches)”
“Small (23-47 Inches)”

Polar T31 Non Coded Transmitter
ECG Accurate

Polar T31 Non-Coded Transmitter
Elastic Strap