Phoenix Contact PSI-REP-PROFIBUS/12MB 2708863 Repeater

The Phoenix Contact PSI-REP-PROFIBUS/12MB, order no. 2708863, is a physical layer repeater for PROFIBUS DP networks based on RS-485. It regenerates the digital signal, compensates for cable attenuation, and extends the maximum segment length. The device supports data rates from 9.6 kbps to 12 Mbps automatically.

Signal Regeneration and Isolation

The repeater provides electrical isolation between segments (2 kV test voltage). It has three independent PROFIBUS ports: two for standard A/B line terminals and one for a stub line or a further repeater. Each port includes short-circuit protection and automatic disconnection of faulty segments. The device also features a built-in terminator network that can be activated via switches for the end of a segment.

Power Supply and Status Indicators

Supply voltage: 24 V DC (19.2-28.8 V), consumption 100 mA typical. Green LED for power, yellow LEDs for data traffic on each port, and red LED for segment fault (short circuit or open line). The repeater is powered via the PROFIBUS connector’s pin 2 (24V) and pin 6 (GND) or via separate screw terminals. The housing includes a removable 2-pin power connector.

Mechanical and Environmental Data

Dimensions: 22.5 mm x 99 mm x 114.5 mm (W x H x D). Weight: 125 g. Mounting: DIN rail NS 35/7.5 or NS 35/15. Operating temperature: -20°C to 70°C. Storage: -40°C to 85°C. Humidity: 10% to 95% (non-condensing). Protection rating: IP20. The housing is made of polyamide PA 6.6 (green for PROFIBUS) with UL 94 V-0 flammability rating.

PROFIBUS Network Topology

With the PSI-REP-PROFIBUS/12MB, a single PROFIBUS segment can be extended from the standard 100 m (at 12 Mbps) up to 1 km when using 10 repeaters (maximum chain). Each repeater also allows branching (star or tree topology), breaking the strict line restriction of RS-485. The device supports up to 31 PROFIBUS nodes per segment (with repeaters counting as nodes).

Installation and Configuration

No software configuration is required; the repeater auto-detects the baud rate by monitoring the bus traffic. DIP switches on the front panel set the terminating resistor (on/off) and the Tx/Rx triggering threshold. The grounding concept: functional earth ground via DIN rail or separate terminal. For high-speed operation (12 Mbps), shielded twisted pair cable (type A) must be used and the total stub length per segment should be < 1 m.