Radio gong
A radio gong is a combination of a radio transmitter and a radio receiver with the function of a doorbell .
business
The radio transmitter is often integrated in the doorbell button or is connected to the doorbell button with a cable. It sends a signal to the receiver as soon as the bell button is pressed. Usually the bell button is attached in front of the entrance door. The radio receiver is attached in the house or, if it is designed as a mobile device, taken into the corresponding rooms or even into the garden.
In Europe, wireless gongs usually operate in the 433/434 MHz band or newer models in the 868 MHz band. The advantage of the 868 MHz band is that it is not yet as "busy" as the 433/434 MHz band and in some band areas it only allows operation in the " Duty Cycle <1% " mode . This means that the devices that use these frequency ranges are only allowed to go on air briefly . And this has the advantage that the number of transmitters that transmit simultaneously ( sources of interference ) is considerably smaller, and the reliability of the desired signaling is correspondingly greater. Very high-quality radio transmitters have additional functions such as triggering an alarm tone and the like.
function
As soon as the radio receiver has received the signal from the radio transmitter, it emits an acoustic signal . The volume is 82–86 dB (A). Devices with below 78 dB (A) are hardly noticeable in the neighboring room.
Some radio receivers also have additional optical signaling. This is done either via very bright LEDs or via xenon flash tubes . Devices with xenon flash tubes are to be preferred, especially for people with hearing problems , because the high light intensity means that they can also be seen if one does not look directly in the direction of the radio receiver. The walls reflect part of the flash, which is perceived accordingly.
Radio range
When it comes to the range of the radio gongs, a distinction has to be made between the radio range (essentially) of the transmitter and the audible range of the sound. "Range" usually means the radio range.
Every wall means a considerable reduction in the radio range. If the wall is made of steel-concrete , the damping is stronger than with brick walls because of the steel reinforcement . If there are several walls, this attenuation is multiplied, so that if, for example, a wall attenuates the radio signal by 75%, from a free field range of 100 meters with 2 walls only a little over 6 meters radio range remains (100 m × 0 , 25 x 0.25). A free field range of 200 meters is already above average; Devices with so-called “ power transmitters ” can even reach 250 to 500 meters.
There are also radio gongs with a so-called " distance multiplier circuit ". This makes it possible to chain several transmitter-receiver combinations with one another so that larger buildings or distances can be bridged.
programming
With some devices it is possible to have a radio receiver react to several transmitters and to assign different melodies to the transmitters via the " individual call " function. Then it can be recognized whether someone is ringing the front door or the back door.
Several radio receivers can also react to one transmitter or several transmitters control different receivers.