Buy Signal

Signals exist to take emotion out of the decision. Setting the condition in advance means the buyer is following a rule rather than reacting to a headline or to the fear of missing out.

The same logic sits behind a treasury policy that buys foreign currency whenever the rate reaches an agreed level. Technical signals are built from price and trading volume.

A common one is a moving average crossover, where the average price over a short window rises above the average over a longer window, which is read as evidence that momentum has turned upwards. Others fire when an asset has been sold off unusually hard relative to its own recent range.

Fundamental signals come from the business rather than the chart. A buyer might set a rule to purchase when a company's shares trade below a target multiple of earnings, or when free cash flow covers the dividend by an agreed margin.

These signals fire far less often and the resulting positions are held far longer. Every signal produces two kinds of error and it helps to name them.

A false positive buys into a move that promptly reverses, while a false negative keeps you out of a genuine rise, and no rule avoids both. Tightening a rule to cut false positives always increases the number of opportunities missed.

Testing a signal on past data is standard, and so is being misled by it. Run enough rules over enough history and some will look brilliant purely by chance, which is why careful users insist on testing a rule on a stretch of data that was never used to design it.

For a non-specialist the practical value is in governance rather than trading. Agreeing the condition that would make the company buy back its own shares, or hedge a currency, converts an argument about market timing into a check against a written rule.