Robert,
It's data, 0's and 1's, just like an Ethernet or 802.11 wireless network, at a specific frequency. Each string of DCS data packets has an engine address and a command.
The data packet replicates each time it's split and each resulting data packed is somewhat diminished/degraded by being split. The following is in somewhat non-technical terms.
On a blocked, star- or home run-wired layout, an engine typically "sees" one set of packets at a time, whereas on a buss-wired, unblocked layout an engine would typically see multiples of the same data packets.
The number of splits and the lack of isolation can cause DCS signal degradation, from the engine's perspective.
