Identify the two common rails
A single bussed resistor network joins repeated resistance elements to one common connection. The named Bourns dual-terminator circuit instead has two common rails, with separate resistance branches associated with the signal nodes. Identifying those two shared connections is the first step in understanding why the circuit cannot be described as an ordinary common-pin array.
The distinction is topological. It concerns which elements share connections, rather than merely how many resistor values appear in a description. A network with two named values could still have a different internal arrangement. The cited circuit drawing provides the relationship between rails and branches, which a detached resistance string or a package description cannot supply.
For comparison purposes, begin with the common connections and then follow the roles of the branches attached to each signal node. This keeps the internal circuit identity visible before considering a part reference. It also explains why a familiar outline or lead count is insufficient: those external descriptions do not state the internal shared paths. The discussion concerns this named drawing, rather than a universal interpretation of every product called a dual terminator.
Retain the ordered R1 and R2 branch roles
R1 and R2 identify ordered branch roles in the Bourns dual circuit. Their labels connect each resistance to a particular side of the topology. Treating them as an unordered pair loses that relationship, even if the same two nominal descriptions remain in a copied list. The question is which role each entry belongs to, not simply whether both entries are present.
That matters because each signal node is associated with branches leading toward different common rails. The role of a branch follows its connection in the circuit. Interchanging the way the two resistance descriptions are assigned is therefore not just a change in presentation; it can describe a different relationship between the node and the rails.
Preserve the R1/R2 order from the applicable part and circuit reference when making a comparison. This provides a clear explanation of the two roles without prescribing values or a termination arrangement for a particular logic family. The cited note contains application examples, but their existence does not turn this topology discussion into an interface suitability decision. The useful result is an ordered circuit description that retains the meaning of both resistance entries.
Match the named dual-terminator circuit identity
The 4100R documentation presents isolated, bussed and dual circuit alternatives. These are not interchangeable descriptions of one internal network. The circuit identity in the ordering information must agree with the corresponding drawing, because that connection pattern gives meaning to the remaining resistance fields.
Read the ordering reference and the internal circuit together. The ordering field identifies the documented alternative; the drawing explains the shared connections and repeated branch arrangement. A resistance entry taken from one alternative cannot explain another merely because both belong to the same package series. Equally, the presence of the series name alone does not identify which internal option is being described.
This is more specific than a general request for a complete part number. It explains which part of that reference resolves the internal topology and why the topology must be resolved before comparing resistance roles. Keep the named drawing as the controlling explanation, rather than importing a code convention from another resistor-network family. The comparison should preserve the relationship between series, circuit alternative and ordered resistance roles instead of flattening them into one apparently self-explanatory resistance label.
Separate branch resistance from parallel measurement paths
An unguarded resistance reading between two terminals can include current paths through several internal elements. In a dual terminator, the remaining branches and common connections form parallel paths around the branch being considered. The meter can therefore see an equivalent network rather than the resistance of one isolated internal element.
The Bourns explanation distinguishes the branch values from the series-parallel resistance presented to an unguarded measurement. This is why an observed terminal-to-terminal value need not reproduce either named branch value directly. The difference follows from the connection pattern, not from an assumption that the component has changed its nominal resistance.
Keep that distinction when interpreting information supplied about a network. A branch specification describes an internal element role, while a terminal reading also depends on the available surrounding paths and measurement method. This guide does not supply guarding connections or calculate an expected reading. Its purpose is to identify why the two descriptions answer different questions, so an ordinary pin-to-pin result is not used as a direct substitute for the documented dual-circuit identity.
Sources and further reading
Named Bourns 4100R circuit identity and dual-terminator explanation only. No termination design, resistance selection, guarded-meter procedure or interface approval is provided.