Design and construction of a carrier-less transceiver based on logic circuit

Thread Starter


Joined Sep 11, 2017
Hello Friends,I need help on a project.Design and construction of a carrier-less transceiver based on logic circuit.Please,kindly share your ideas on it.

Contents of attached Word file:
TITLE Design and Construction of a Carrierless Transceiver based on Logic Circuits (EGBOWON DARE JOSEPH_140403037)

The design of this Prototype is such that we multiplex the clock and data with an AND gate 74LS08 and demultiplex the received signal with a negative edge-triggered JK flip-flop 74LS112. Prototype 3 does not transmit the carrier.

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This appears to be serial to IR or visible light converter. When you say carrierless, I assume you actually mean self-clocking. Something like Manchester encoding. Is this correct?


Joined Feb 24, 2006
Clearly the TS doesn't understand what is going on and cannot explain what the circuit is supposed to do. I have stared at it for a while and cannot fathom what is going on either. Almost 2 months has gone by so apparently nobody else knows or cares what is going on. The poor quality diagram and the inability to know what some of the part numbers are contributes to the difficulty.


Joined Sep 22, 2013
Smoke signals........or flag waving.

What is a carrier-less transceiver? In the old days a carrier referred to an RF signal.

But anything, that you can impress information on, is a carrier. Like voltage or current.

Or a pigeon.
In the upper right quadrant there is a USB to serial converter which is attached to a MAX232. The MAX232 converts the RS232 signal to digital logic levels. The transmit line from the MAX232 goes to a couple of ICs in the lower right quadrant. One of these is a 1.84 MHz oscillator that is used to modulate the logic level serial data. This is provides some immunity from light noise but is unusual in that the frequency is several times the normal values used in IR remote controls and other IR transmitters. Typically they are around 40KHz +-. The modulated signal is sent to an LED ( not shown) The drive circuit is shown directly below the MAX232.
In the upper left is a photodiode feeding a series of ICs (probably provide amplification) that also feed a couple of ICs in the lower right corner. The 74LS112AN demodulates the incoming signal using the same 1.84MHz signal and sends it through the 74LS04 back to the MAX232. The photodiode is a visual light receiver instead of IR.

With two of these and a couple of visible light lasers you could make a line of sight serial data link.