The ESi ESRTP4RF+ Wireless Programmable Room Thermostat Receiver Unit (A775) is a sleek white rectangular-shaped device that operates on battery power using AA batteries. Its wireless design allows for easy installation with wall mounting capabilities. This programmable thermostat offers 7 days of programming options and utilizes temperature sensor technology for accurate heat control. With a voltage of 230V and line voltage compatibility, this ESI branded thermostat is a convenient and efficient choice for maintaining a comfortable home environment.