Elevator as Half Duplex Analogy | Generated by AI
Question: No, I mean that an elevator, at any one point in time, can only move either up or down (not both directions simultaneously), so it is half-duplex in that analogy.
Answer:
Yes, that’s a very reasonable and commonly used analogy.
In communication theory:
- Half-duplex = two parties / directions can communicate, but not at the same time. One must wait (or yield) while the other is active. Classic examples: walkie-talkies, many older intercoms, turn-based chat.
The elevator direction behaves the same way:
| Property | Full-duplex communication | Half-duplex communication | Elevator movement |
|---|---|---|---|
| Can both directions be active simultaneously? | Yes | No | No |
| Directions / parties | Both can send & receive at once | Only one can send at a time | Only one direction (up or down) at a time |
| Switching | No need to switch | Must switch / take turns | Must reverse direction to change |
| Resource sharing | Separate channels / full bandwidth both ways | Shared medium / channel | Shared shaft / hoistway |
| Real-world intuition | Telephone call | Push-to-talk radio | Single elevator car in a shaft |
So when people say “the elevator is half-duplex”, they are usually not talking about the emergency intercom, but using the physical motion of the elevator car as a teaching analogy for half-duplex communication.
This analogy appears quite often in:
- Networking textbooks and lectures (especially when explaining why Ethernet hub networks were half-duplex)
- Operating systems / concurrency lectures (shared resource that can only serve one direction at a time)
- Informal engineering & computer science discussions
Quick examples of the analogy in use:
- “Think of a single-lane bridge or an elevator: only one direction of traffic at a time → half-duplex.”
- “A half-duplex link is like an elevator in a building — it can go up or down, but not both at once.”
Your interpretation is correct and widely understood in exactly that sense.
References:
- None (this is a standard conceptual analogy taught in computer networking and does not rely on a specific external source)