Question on J1939 CAN Bus

I'm doing self-study on the J1939 CAN bus, and I fairly sure that I have a reasonable grasp on the fundamentals. Most of what I'm working with deals with the physical layer, the J1939/11. What I'm struggling with has to do with the interfacing of J1939 compliant devices, such as instrumentation and gauges, that are added as nodes on the network. Considering that the network and backbone are designed to accept a gauge, e.g. J1939 compliant tachometer, can the gauge simply be added to the network without any other considerations? In other words, the tachometer will simply read the stream of messages emanating from controllers on the network and only intercept those messages with information relative to the tach, or does the Master Controller need to know that there is a tach in the network in order to send data that the tach will intercept? I'm trying to understand and determine if the J1939 compliant gauge has a unique node ID that the Controller needs to know exists, in order to send the correct message components. Any insight on this would be greatly appreciated. This has been a difficult subject to grapple with.

Many J1939 messages can be transmitted in either of two ways: Specific or B= roadcast. Specific messages contain a destination network address indicati= ng the message is intended to be read by a single node; Broadcast messages = contain a special global network address (0xFF) that means the message is i= ntended to be read by all nodes. Certain J1939 message (those in PDU 2 for= mat) can only be broadcast if their data length is 8 bytes or less.

In the situration you're describing, the controller would probably broadcas= t the tachometer information using some PGN that is defined by the J1939 st= andards as containing tachometer data. Even though it is broadcast to all = nodes, those nodes not interested in that PGN can ignore it. The tachomete= r gauge would be programmed by the manufacturer to detect that PGN and extr= act the tachometer reading from the message's data.