Signal Aspect Flashing Relay (SAFR)

RSP’s Signal Aspect Flashing Relays (SAFR) are the only Network Rail Accepted Product to replace the old Flashing Aspect Control Unit (FACU).

RSP’s Signal Aspect Flashing Relays Key Features:

• Railway Cat No. 086/009191
• RSP Part No. DLL05246
• Compliant to NR/SP/SIG/100
• Compatible with both incandescent and LED Signals
• Quick and easy installation with base and unit designed and built to fit into
  standard BR930 relay slot
• Adaptor plate available to allow quick and easy replacement of an old
  FACU module
• Supplied fully certified and factory-tested for improved reliability.

What is a Signal Aspect Flashing Relay (SAFR)

A Signal Aspect Flashing Relay (SAFR) is a relay used in railway signalling systems to control the flashing of signal aspects, typically yellow lights, to provide advance warning to drivers.

In traditional relay interlockings, the SAFR would be a dedicated timing relay within the relay room. In modern computer-based interlockings, the flashing function is often implemented in software, although the term SAFR is still commonly used by signalling engineers to describe the flashing aspect function.

What does it do?

The SAFR repeatedly switches a signal lamp on and off at a predetermined rate, creating a flashing effect. This is commonly used where:

• A train is being routed onto a diverging route at speed.
• Drivers need additional advance warning that the route ahead differs from the normal straight-through route.
• Junction signalling requires flashing yellow sequences to indicate the train can proceed over a diverging route without stopping.

How does a SAFR work?

The relay:

1. Receives an input from the signalling control circuits.
2. Energises and de-energises at a set frequency (typically around once per second, depending on the signalling design).
3. Causes the associated signal aspect to flash on and off.
4. Is interlocked with other signalling relays to ensure flashing aspects are only displayed when it is safe to do so.