In ARINC 429 where are the bits indicating the hex value of Equipment ID?
ARINC 429 is a unidirectional one-to-many (broadcast) transfer bus with a maximum of 20 receivers.


SourceDesign with four unidirectional ARINC 429 buses

There is normally little need to identify the source, as there is only one. So there is no field in the protocol word dedicated for ID transmission. As visible in the previous image, bidirectional exchanges require two buses and several ports to connect them. The receiving unit (LRU) can determine from the port used which source feeds the bus.

However label 377 (octal) can be used to transmit, from time to time, the equipment ID if desired. Example: ID 10D (hex):

  

Source: ARINC specifications

Note: On the other hand, SDI bits can be used by the source to select the receiver.