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You can buy ready made RF transmitter and receiver modules from digikey and other sources. The cheapest way is to not use coding. Just use carrier detection. The door bell switch is in series with the battery to the transmitter. The receiver output triggers a power mosfet in series with the buzzer. (That is if the buzzer is operating from DC.) If you discover false buzzes, you will have to use the coding module for the transmitter and receiver which uses an 8 bit code word. These are also available from the supplier of the TX and RX modules. One thing to look out for is where the transmitter module/antenna is placed. Some high security doors have a metal sheet that will block the transmissions if you put the module on the door.
I'm a newbie in RF, really I'dont know nothing about RF, I need to make an RF transmitter and a RF receiver at any frecuency with out an RF module.
I'm using the IC UM3750 and I want to implement the RF circuits for this application.
Could you help me to modify these circuits to do that?
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Better check the mother Electronics Link from where original text resides. 27MHz Links
Look, This Page 2 have the Cordless bell workings. But the first and third page gives all related information.