The basics

Logic gates are the basic building blocks of digital circuits
(and therefore digital devices)

In an abstract way, they consist of a functional box
with a specific number of input signals
(normally one or two)
that processes them with a specific logic function
(i.e. boolean,
i.e. with a range of two possible values
1 or 0
ON or OFF)
and gets a result as an output signal.

Internally they are very simple
and can be implemented either mechanically
(e.g. with valves and pipes)
or electrically
(with switches or transistors)

Their power come when they are combined.
A digital computer contains billions of them.
Complexity emerges out of simple units.

Without having to use billions of them
Combining them can yield interesting results.
For example,
even a few of them can perform
Arithmetic and Logic operations.

A machine that adds two numbers
Made out of logic gates
Doesn’t know that it’s adding two numbers.
Each of its gates acts according to their rules.
They don’t know that together they are adding two numbers.
However, all together as a whole system,
They ARE adding two numbers.

How could we replicate this phenomenom with human powered logic gates?

Postcards prototype

On one hand, I want to explore the idea with humans that are in the same room.
However, I also thought of this idea of humans that are not in the same room.
This is the idea that I want to try first.

For this, the signals would be postcards sent in the mailing system.

A Digital Architect (myself, for the moment)
would devise a specific logic circuit with a function.
For example the following diagram corresponds to the operation
of “calculating” if a given number of 3 bits
Is prime (1) or not (0)

Each participant would be a logic gate, and therefore
It would have a specific logic function
That they would apply to the input(s) that they receive.
They would also have a destination(s) for their output(s).
They wouldn’t need to know where they are in the circuit.

(It may be more interesting if they didn’t know where they are
AND if they didn’t know the function of the circuit.)

The setup

After devising the digital architecture, we need the mail addresses of each participant.

Each participant will need the following. This could be also mailed in an envelope.

  • The truth table that they will follow, i.e. the output that they have to have when receiving a specific input (e.g. if you receive two postcards with “1” in them, your output will be “1”, if any of them or both have a “0” in them, your output will be “0”)
  • Prepaid postcard(s) with the address(es) of the following gate(s) – We can call these the output postcards
  • A camera to photograph the postcard(s) that they receive and they send (for documentation purposes)

The execution


To start the computation, the Input (I) person (myself, for the moment)
will encode an input in binary form,
will write a bit (1 or 0) in each corresponding postcard,
will send the first postcards to the human logic gates through the mailing system,
and (optionally) will let the participants know that the [first] iteration has started.

Logic gates

A participant eventually will receive the [input] postcard(s)
with the digital signals (bits)
that they need to complete their logic operation.
These may arrive in different days, and/or after many days
after the execution started.
They should log when the postcards arrive.

Whenever they have the postcards they need,
they have to execute their operation
and write the result in their [output] postcard(s).
They should photograph their input and output postcards together.

After that, they have to send their output postcard(s)
through the mailing system.


Eventually, the last logic gate(s) will send their outputs
to the Output (O) person (myself, for the moment).
This person would then be able to assemble and decode the result of the computation,
and the process would have finished.

Call for logic gates (2017-09-16)

Let’s create a computer through the mailing system (Postcards Computer!)


I’m working with the idea of Human Powered Computation Machines (more info here) and I want your help creating and testing a prototype: a Human Powered Computation Machine that works through the mailing system.

You can read more about it here. Basically each person would perform a very simple logic operation, and we will receive and send digital signals through postcards. The complexity will emerge based in the abstract architecture that will connect us.

I need the help of some of you working as participants of this computer. If you are interested send me your mailing address through a personal [electronic] message (off list).

If you want to contribute with the postage, I’ll be happy to accept cash donations or through the Cash app (sejomagno).

Thank you!