Using a keypad challenge — swipe-card reader sends to control program

If we invert the relationship, here's what happens:

1. A big delay occurs until the next person swipes their card.
2. Swipe sends message “Swipe card ID # xxxx was swiped.”
3. Control replies with “Challenge the user with YYYY.”
4. A delay occurs while the user types in the response.
5. Swipe sends message “Challenge response is IZZY.”
6. Control replies with “OK, change LED to GREEN.”
7. A 20-second delay occurs, while the door is opened.
8. Control sends a pulse “Change LED to RED.”

In this case, there was one pulse and two messages.

So, by carefully analyzing the transactions between your clients and servers, and by being able to carry useful data within pulses, you can make your transactions much more efficient! This has ramifications over a network connection, where message speeds are much slower than locally.