# Heartbeat 3

Only the **Heartbeat 3 period** can be defined - by changing the value of register 0x64. Standard *SimpleTime* encoding is used. The third heartbeat can be used in [*basic WiFi-enabled user modes*](/kb/simple-api-6-generation/modes/wifi-user-modes.md), [*WiFi Atlas user modes*](/kb/simple-api-6-generation/modes/api-6-wifi-atlas-user-modes_15269894.md) and [*WiFi Precise user modes*](/kb/simple-api-6-generation/modes/api-6-wifi-superlocal-user-modes_15466519.md) to define a regularly transmitted message with MAC addresses.

| **Mode type** | **Heartbeat 3 message**                                                                                                                                                               |
| ------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| WiFi          | <p>Two messages are sent with 3 MAC addresses total (1,5 each),<br>the <strong>0xE0</strong> event is sent in the first and the <strong>0xE1</strong> event in the second message</p> |
| WiFi Atlas    | <p>The <strong>0x6B</strong> event is sent in the first message and two MAC addresses<br>in 12 bytes are sent in the second message</p>                                               |
| WiFi Precise  | <p>Only one message is sent with the event <strong>0xD2</strong> in the second byte<br>followed by 5 MAC pointers and the respective RSSI</p>                                         |

Heartbeat 3 was also created to control the Stupid modes (0x12 and 0x61).

In [*Stupid mode 1*](/kb/simple-api-6-generation/modes/api-6-standard-user-modes_15400961.md), one single uplink event with two MAC addresses will be sent regularly (similar to the behavior of WiFi Atlas modes) - the period is defined by this heartbeat. In [*Stupid mode 2*](/kb/simple-api-6-generation/modes/api-6-standard-user-modes_15400961.md), an empty message with Sigfox metadata only is sent regularly according to the heartbeat period.

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