# Talk:Causal system

## Help..what is NON-causal?

the only thing I can think of is a digital filter that because of delays, gets hi-frequency information before the pulse 'hits'. PLEASE talk about this. CorvetteZ51 (talk) 09:03, 16 April 2017 (UTC)

## Incorrect example in article

The article lists: y \left( t \right) =x(-t) as an example of an anticausal system...this is only true is t<0. For instance, let t=1. Then the value of the output signal at t=1, y(1), is determined uniquely by the input signal at time t=-1, i.e. x(-1). This is clearly causal. —Preceding unsigned comment added by 130.15.81.250 (talk) 19:16, 15 February 2011 (UTC)

## Status of Article

I happened to be studying for a Signals & Systems exam, and I noticed this article was a bit hard to understand. So, I went ahead and tried to make the first paragraph a bit clearer, but I don't have the time to make the mathematical notation clearer. I hope there is someone out there that can do that.

Good Luck, Pg8p 08:41, 14 December 2006 (UTC)

## Example Suggestion

This article could do well with a basic example to illustrate the concept more clearly. A graph and a few equations would go a long way.

Good Luck, Pg8p 08:41, 14 December 2006 (UTC)

## Causal vs. Memory Systems?

Is there any difference between causal and memory systems?

This information from System analysis... hope it helps
• Memoryless systems do not depend on any past input.
• Systems with memory do depend on past input.
• Causal systems do not depend on any future input.
Best,
Pg8p 08:41, 14 December 2006 (UTC)

## Dependence on the output?

y(n)= y(n-1)+ x(n) seems also causal, nevertheless the definition does not include such a case. Can we make a solid statement on that? (My textbook could not clarify it either.) —Preceding unsigned comment added by Fonduesuisse (talkcontribs) 13:19, 11 October 2007 (UTC)

## Mathematical DefinitionS

It should be explained, that in this paragraph two definitions of causality are shown. —Preceding unsigned comment added by 134.130.44.166 (talk) 18:08, 8 November 2007 (UTC)

Should the first mathematical definition include a "for every ${\displaystyle t_{0}}$"? It seems the current definition is actually giving conditions for when a system is causal at ${\displaystyle t_{0}}$. The condition given needs to apply at all ${\displaystyle t_{0}}$ in order for the system to be causal, right?