The CX1000 is a transmitter compatible with the DA50L-A (TXRX1000A) that servers as a push button or a door/window magnetic contact.
Rodann Electronics TX1000A-PB Push Button & Door Contact for DA50L-A
Use this transmitter as a push button or door window contact with the DA50LR-A receiver. Simply mount the door / window contact on the door you would like to monitor and when the door is opened, the sensor sends a radio signal to the receiver, up to 500 feet away. Or, use the product as a push button. When the visitor pushes the button, the transmitter sends a signal to the receiver and it plays a chime sound.