The 902-928 MHz model requires line-of-sight but is more resistant to electrical noise. Handheld transmitters are available in 8, 4, 2, and 1 buttons in a heavy-duty aluminum enclosure. Receivers are available with 8, 4, 2, and 1 relay outputs (5A at 250V contact rating) in a plastic NEMA 4x enclosure. Includes antenna, mount, and coaxial cable. Performance Guaranteed.