An audio alarm (if switched on) and visual indicators alert you when you are training above or below your heart rate zone limits.
Stop watch
Basic time keeping: Time, date and alarm
Backlight
Wireless heart rate monitor (ECG accurate) with an analogue chest strap transmitter and a wrist watch receiver
Wrist watch receiver has a small case size and thin straps for small wrists
Battery for chest strap transmitter is user-replaceable.
It can work with gym equipment (e.g. treadmills) capable of picking up your transmitter's signals to show your heart rate on the equipment's display panel
The SE200 does not possess the following basic features: Average heart rate, maximum heart rate of exercise session.
Summary
The Oregon Scientific SE200 heart rate monitor is one of several Oregon entry level heart rate monitors. It has pretty much the same features as the Oregon HR102. The feature that distinguishes itself is that it is small size wise. Hence it is particular suitable for women with small wrists.
Note: The Oregon SE series is not arranged in increasing order of complexity and price, which is a bit unusual and deviates from normal practice. In this case, the SE128 is a more advanced heart rate monitor than the SE200.