In punched or perforated card key system for the identification of timber, a card has:
A Physical Database for Wood
The punched-card key system is a clever, non-computerized method for identifying wood species. Think of it as a physical database. Each card in a deck represents a single species of wood. The card has a series of numbered holes around its edges, with each hole corresponding to a specific anatomical feature (e.g., pore size, ray type, color, etc.).
To identify an unknown wood sample, an observer notes its features. For each feature present, the corresponding hole on the card is notched out, creating an open slot. By passing a long needle through a specific hole in the entire deck of cards, the cards for species that have that feature (i.e., the notched ones) will fall out, narrowing down the possibilities until the species is identified.
📝 Detailed Analysis of the Options
(a) 72 holes, (b) 92 holes, (d) 100 holes
These are incorrect. The standard system developed and widely used for timber identification does not use these numbers of holes.
(c) 96 holes
This is the correct answer. The standard punched-card system for timber identification, as developed by institutions like the Forest Products Research Laboratory (FPRL) in the UK, uses a card with 96 holes. These holes represent a comprehensive set of macroscopic and microscopic features required to distinguish between a vast number of wood species.
📊 How the Punched-Card System Works
| Component | Function |
|---|---|
| Card | Represents a single, specific wood species. |
| Hole | Represents a specific anatomical feature (e.g., "Pores in radial chains"). |
| Notch (or Perforation) | Indicates that the species on the card possesses that specific feature. |
| Sorting Needle | Used to physically sort the cards by passing it through a specific hole. |
💡 Study Tips
- Memorize the Number: For exam purposes, 96 is the specific historical number to associate with this timber identification system.
- Hole = Feature: Remember the core concept: each hole stands for a distinct physical characteristic of the wood.
- Notch = "Yes": A notched hole is like a "yes" answer to the question, "Does this wood have this feature?"