| Very Low-Cost Sensing and Communication Using Bidirectional LEDs Recent countries visiting this post |  |
 | 9 | United States |
 | 3 | |
 | 1 | Poland |
| Very Low-Cost Sensing and Communication Using Bidirectional LEDs Recent countries visiting this post | |
| 9 | United States |
| 3 | |
| 1 | Poland |