The SF501ES Single Button and SF501/2ES Dual Button Call Transmitter pendants feature the great range and reliability of 900 MHz in a small, water-resistant package. Users can wear a pendant in the shower or bathtub, outside in the rain, or other environments where the pendant may be splashed with water or momentarily submerged. The SF501ES has a single-button design with "press and one-second hold" activation, making the product very easy to use, yet still reduces false alarms. The SF501/2ES has a two-button design with "press both buttons at once" activation to further reduce false alarms. When a transmitter is activated, it continues to send an alarm signal until its reset button, located on the back, is pressed.

The transmitters are especially suited for assisted living installations. Weighing less than 1.4 ounces each, they include both a neck cord and a belt clip, and can easily be converted by the end user. An optional wristband allows a pendant to be worn on the wrist or arm.

The transmitters feature a fully supervised RF link to ensure reliability. The built-in LED flashes with all transmissions, including supervision, so the user can see that the transmitter is still functioning. The battery is a customerreplaceable 3V lithium type.