Why re-invent the wheel?
Why design a project from the start when there are many modules available on the web that can get a project finished in half the time.
One such module is a 4-Channel remote control.

The Transmitter plus the Receiver costs $5.00
The range is about 30 metres.

TRANSMITTER / RECEIVER SPECIFICATIONS Transmitter: 1.Operating voltage: DC12v (27A/12v battery) 2.Operating Current: 10mA @ 12v 3.Radiated power: 10mw @ 12v 4.Modulation mode: ASK (Amplitude Modulation) 5.Transmitting frequency: 315MHz 6.Transmission distance 50-100M (Open field, receiver sensitivity  -100dbm) 7.Encoder types: fixed code Receiver Board Operating voltage DC 5v, receiver sensitivity -98db. VT, D3, D2, D1, D0, +5v, GND. VT is a valid signal high output pin. Upon receiving a valid signal, this pin goes HIGH. Can be used to drive a relay. D3, D2, D1, D0 are the 4 outputs.  One of the outputs goes HIGH when a valid signal is detected.

The transmitter is a fob-sized case with four buttons.
These buttons can be labelled A, B, C, D or D, C, B, A depending on the manufacturer and the software has to be written for each type of transmitter.
The receiver is a very small PC board with the output via a set of pins.
But the transmitter/receiver set-up needs additional circuitry to take the 4 outputs to control various devices.
It needs either a set of relays or buffer (DRIVER) transistors.

That's what this project does.
It takes the 4 outputs and connects them to a set of 4 driver transistor.
But an additional feature is provided by the microcontroller.
It turns each of the outputs ON or OFF each time the button is pressed.
This project is ideal for so many applications.
You may have a large train layout and you will be able to control 4 items at a distance without the need for wiring.
Or you can open and close gates or animal feeders or watering devices.
You can turn on displays or alarms or anything that needs activation.
The transmitter will work up to about 30 metres and operates at 315MHz via a transmitting module contained in a 3-leaded metal can, soldered next to the transmitting coil.

 
The CIRCUIT

 4 channel remote control circuit

CONSTRUCTION
The components fir on a small PC board and all parts are through-hole, except for the surface-mount LEDs.

4 CHANNEL REMOTE CONTROL PCB

The PROGRAM
The program only performs a very simple task but doing this with discrete devices will take at least 6 chips.
You need to detect a long or short tone from 4 channels and provide a latching circuit.
Rather than sit down and design the necessary circuit, you can use a microcontroller.
It's just a very convenient way of solving your circuit-designing problems.
The outputs of the receiver are fed to a 100n capacitor via different-value resistors.
The diodes are needed because the outputs go low and the resistors not being used would be taken to 0v and have the effect of reducing the line that is HIGH.
If the 120k line is HIGH and all the others are LOW, a voltage-dividing situation would result in a very small voltage on the 100n.
With our arrangement, the voltage on the 100n will be 5v, but the time taken to reach 5v will be different for each line as the value of the charging resistor is different.
The micro discharges the 100n via the 220R and then waits to see how long it takes to charge the 100n.
It then discharges the 100n and waits again.
It keeps doing this to determine if a button has been pushed for a short period of time or long period of time.
This arrangement has been done because we only have 6 in-out lines on the PIC12F629 microcontroller chip and 4 lines have been allocated for the outputs.
The fifth line is INPUT ONLY and does not have the capability of discharging the 100n.
That means we only have one line available to detect the 4 input lines (as we need to have a line that can be configured as input and output). 
Many of the sub-routines for this project have already been written and you can look through previous projects for the instructions.
The micro will be mainly looping around the input. This is called "polling" the input and it simply discharges the 100n and waits for a long period of time to see if it has charged. This period of time represent the time taken for the 120k to charge the 100n. It is only a few milliseconds, but in computer time this is considerable.
When the 100n is detected as being charged, the micro goes to a sub-routine to determine which line is HIGH.
The program then toggles the corresponding output.
 

MORE
For more details on modifying the program and burning the PIC chip, see Talking Electronics website and click on Elektor,EPE,Silicon Chip in the index.
You can find details of:  PICkit-2 and Adapter connected for In-Circuit Programming at this link.


Here is the file you will need for "burning" your chip and/or modifying the program. It comes as .asm, .txt and .hex for using as a file to modify, or to read, or to burn a new chip:
4Ch-303MHz.asm
4Ch-303MHz.txt
4Ch-303MHz.hex
The kit comes with a pre-programmed PIC chip, see parts list below.

;**************************************************************** ;Started 18/4/2015 ;4-Channel 303MHz (313MHz)- Press one of 4 buttons for ;a short time and the corresponding output will toggle. ;**************************************************************** list p=12F629 radix dec include "p12f629.inc" errorlevel -302 ; Don't complain about BANK 1 Registers during assembly __CONFIG _MCLRE_OFF & _CP_OFF & _WDT_OFF & _INTRC_OSC_NOCLKOUT ;Internal osc. ;_MCLRE_OFF - master clear must be off for gp3 to work as input pin ;**************************************************************** ; variables - names and files ;**************************************************************** temp1 equ 20h ; temp2 equ 21h ; temp3 equ 22h ; temp4 equ 23h ; _flash equ 26h ;for flashing the LED ;**************************************************************** ;Equates ;**************************************************************** status equ 0x03 rp1 equ 0x06 rp0 equ 0x05 GPIO equ 0x05 status equ 03h option_reg equ 81h ; bits on GPIO pin7 equ 0 ;GP0 Input from 303MHz module pin6 equ 1 ;GP1 Output A pin5 equ 2 ;GP2 Output B pin4 equ 3 ;GP3 not used pin3 equ 4 ;GP4 Output C pin2 equ 5 ;GP5 Output D ;bits rp0 equ 5 ;bit 5 of the status register ;**************************************************************** ;Beginning of program ;**************************************************************** org 0x00 nop nop nop nop nop SetUp bsf status, rp0 ;Bank 1 movlw b'11001001' ;Set TRIS GP1,2,4,5 out GP0,input movwf TRISIO ; bcf status, rp0 ;bank 0 movlw 07h ;turn off Comparator ports movwf CMCON ;must be placed in bank 0 clrf _flash clrf GPIO ;Clear GPIO of junk goto Main ;********************* ;* delays * ;********************* ;approx 16uS delay _10uS goto $+1 goto $+1 goto $+1 goto $+1 goto $+1 goto $+1 goto $+1 retlw 00 _XuS movlw .100 movwf temp1 _2 nop decfsz temp1,f goto _2 retlw 00 _1mS movlw .2 movwf temp2 _1 nop decfsz temp1,f goto _1 decfsz temp2,f goto _1 retlw 00 _100mS movlw .100 movwf temp2 _100 nop decfsz temp1,f goto _100 decfsz temp2,f goto _100 retlw 00 _500mS movlw 0FFh movwf temp2 _500 goto $+1 goto $+1 decfsz temp1,f goto _500 decfsz temp2,f goto _500 retlw 00 ;**************************** ;* Sub Routines * ;**************************** LED bsf gpio,1 call _500mS bcf gpio,1 call _100mS decfsz _flash,1 goto LED call _500mS call _500mS call _500mS call _500mS goto Main Toggle decfsz _flash,1 goto $+4 movlw 02 xorwf gpio,1 ;pin6 button A (1) goto M2 decfsz _flash,1 goto $+4 movlw 02 xorwf gpio,1 ;pin6 button A (2) goto M2 decfsz _flash,1 goto $+4 movlw 04 xorwf gpio,1 ;pin5 button B (3) goto M2 decfsz _flash,1 goto $+4 movlw 04 xorwf gpio,1 ;pin5 button B (4) goto M2 decfsz _flash,1 goto $+4 movlw 04 xorwf gpio,1 ;pin5 button B (5) goto M2 decfsz _flash,1 goto $+4 movlw 10h xorwf gpio,1 ;pin3 button C (6) goto M2 decfsz _flash,1 goto $+4 movlw 10h xorwf gpio,1 ;pin3 button C (7) goto M2 decfsz _flash,1 goto $+4 movlw 10h xorwf gpio,1 ;pin3 button C (8) goto M2 decfsz _flash,1 goto $+4 movlw 20h xorwf gpio,1 ;pin2 button D (9) goto M2 decfsz _flash,1 goto $+4 movlw 20h xorwf gpio,1 ;pin2 button D (10) goto M2 decfsz _flash,1 goto M2 movlw 20h xorwf gpio,1 ;pin2 button D (11) goto M2 ;**************************************************************** ;* Main * ;**************************************************************** Main bsf status, rp0 ;Bank 1 bcf TRISIO,0 ;make pin7 output bcf status, rp0 ;bank 0 bcf gpio,0 ;make pin7 low to discharge 100n call _1mS ;discharge 100n bsf status, rp0 ;Bank 1 bsf TRISIO,0 ;make pin7 input bcf status, rp0 ;bank 0 nop btfss gpio,0 goto $-2 bsf status, rp0 ;Bank 1 bcf TRISIO,0 ;make pin7 output bcf status, rp0 ;bank 0 bcf gpio,0 ;make pin7 low to discharge 100n call _1mS ;discharge 100n clrf _flash bsf status, rp0 ;Bank 1 bsf TRISIO,0 ;make pin7 input bcf status, rp0 ;bank 0 btfsc gpio,0 goto Toggle incf _flash,1 call _XuS goto $-4 ;switch debounce: M2 bsf status, rp0 ;Bank 1 bcf TRISIO,0 ;make pin7 output bcf status, rp0 ;bank 0 bcf gpio,0 ;make pin7 low to discharge 100n call _1mS ;discharge 100n bsf status, rp0 ;Bank 1 bsf TRISIO,0 ;make pin7 input bcf status, rp0 ;bank 0 call _1mS call _1mS btfsc gpio,0 goto M2 goto Main END