NuTone Extra Doorbell Transmitter for 224WH Wireless Door Strobe / Chime System Price $22.06 Add this extra NuTone wireless doorbell transmitter to your 224WH Wireless Door Strobe/Chime System (NT-224WH) to identify one door from another. Read more about NuTone Extra Doorbell Transmitter for 224WH Wireless Door Strobe / Chime System