Point-to-point Ethernet and industrial Ethernet switches are often treated as competing options when wiring a plant floor. In most cases they are not substitutes for each other — they are two ways to connect the same devices at different scales. No protocol expertise or bandwidth math is needed to choose between them. Count how many devices on site need to talk to each other, and the answer follows.
A developer once built an open-source tool for transferring large files directly between two devices. The idea behind it is plain: when only two endpoints are involved, data travels straight from A to B without intermediate hops — the simplest setup and the most controllable one.
Industrial sites have the same kind of scenario. One RS485 device hands its data to another device, both sit in fixed positions, and no third device will be added in between. Point-to-point is enough. The setup is straightforward: fit each device with a serial port to ethernet adapter, for example the USR-TCP232-410s, and configure one end as TCP Server and the other as TCP Client. Serial data on both sides is then transparently bridged over Ethernet. The 410s carries one RS232 and one RS485 port that work simultaneously, with baud rates from 600 bps to 230.4 Kbps — a range that covers most field equipment.
Point-to-point earns its place on two counts: data never passes through a third device, so latency and failure points stay minimal, and one switch is saved along with simpler cabling.
The scenarios that fit it share two features:
① there are exactly two communication endpoints;
② the link is fixed, with no expansion planned in the near term.
Production lines rarely stay at two devices forever. Add an HMI, add a SCADA host, or start viewing the same device's data from an office PC, and the point-to-point link is stuck — the new device has no port to plug into.
At this stage, the practice is to give every serial device a serial port to ethernet adapter and converge all the cables into an industrial switch. The USR-ISG series offers 5/8/16-port gigabit models, fanless, with aluminum housing, IP40 protection, DIN-rail mounting, a -40℃~85℃ operating range, redundant dual power supplies, and 6 kV surge protection. Once online, the host reaches any device by IP address; adding equipment only consumes one more port, and existing wiring stays untouched. The 410s also handles Modbus RTU/TCP conversion, so serial instruments can be read by PLCs and SCADA hosts directly over Modbus TCP.
The difference between the two setups is topology: point-to-point is one-to-one, while a switch turns the network into many-to-many. Two checks settle whether a switch is needed: whether three or more devices already need to talk to each other, or whether expansion is known to be coming. If the answer is yes, put the switch in now — re-cabling later costs more than a port today.
In water utilities and fire protection projects, data from multiple field devices has to reach a single monitoring center. The USR-TCP232-410s supports TCP Server mode, letting each device establish its own connection while the center receives all of them; in electric fire alarm systems, alarm sensors connect through the 410s over RS485 and alarm messages are pushed to a remote server in real time. This many-to-one architecture depends on a switch to converge every device onto one network.
For lines where downtime is unacceptable, ring redundancy deserves a look. Certain USR-ISG models run on the ERPS protocol: when the primary link fails, the backup path self-heals within milliseconds (on the order of 20 ms), so a single broken link will not take down the whole network. Point-to-point cannot provide this.
① Count the devices: two fixed endpoints → point-to-point; three or more, or expansion planned → switch.
② Count the usage: data flows only between the two → point-to-point; SCADA hosts, monitoring centers, or remote access involved → switch.
③ Count the reliability: brief outages are acceptable → either works; outages are not → switch with ring redundancy.
Point-to-point is not a lite version, and a switch is not an upgrade. At a scale of two, point-to-point is the correct answer; the switch proves its value once the network grows. Count first, then choose.
Three checks apply at purchase time. For the industrial switch: verify 3C, CE, FCC, and ROHS certifications, and confirm the temperature range and power input range (the USR-ISG accepts DC 9.6~60 V). For the serial port to ethernet adapter: confirm the working modes (TCP Server/Client, UDP) and serial interface types cover the field devices. For most line scenarios, one USR-TCP232-410s plus one USR-ISG co
