The button supports up to 20PCS, and the receiver supports up to 100pcs.
If multiple buttons are paired with one or more receivers in the same system, each button can be set to a different ringtone.
Power-off memory function: Turn the power on again after power off, no need to re-adjust and lock the ringtone.
The transmitter has no screw chuck design, and it can be waterproof and dustproof without rubber ring.
The transmitter USE a 23A12V alkaline battery (not included battery).