The Alpha Communications WPT501 Single Button Call Pendant Transmitter features the great range and reliability of 900 MHz in a small, water-resistant package. Users can wear the pendant in the shower or bathtub, outside in the rain, or other environments where the pendant may be splashed with water, or momentarily submerged. A single-button design with "press and one second hold" activation makes the pendant very easy to use, yet still reduces false alarms. When the WPT501 is activated, it continues to send an alarm signal until its reset button, located on the back, is pressed.