Solutions for railway signalling

SITE's internal division processes and patents systems for railway control, developing solutions for the safety and movement of the carriages through integrated systems.


The B.A.c.c. is a system used to guarantee the minimum safe distance between trains on double track lines, which gives the driver advanced and continuous visibility of the signal ahead and which causes automatic breaking of the locomotive if a stop signal is ignored.
External Dimensions of Protective Cabin:
  • Length: 1900 mm
  • Height: 2430 mm
  • Depth: 1900 mm
  • Weight of fibreglass signal box (empty): 340 kg
  • Material: fireproof fibreglass
Internal Dimensions:
  • Length: 1635 mm
  • Height: 2200 mm
The system is based on track circuits with coded currents (block sections); those tracks circuits are fitted with impedance bounds and they are approximately 1350 meters long, up to a maximum length of 2000 m. The system uses fibre glass signal boxes placed near track signals, which contain the equipment necessary to receive and generate codes and which can change the aspect of the signal according to those codes.
  • on tracks with speeds no higher than 200 km/hour, there are four codes: 75-120-180-270 on a carrier frequency of 50Hz
  • on tracks with speeds higher than 200km/hour, there are five additional codes originating from the composition of the 4 codes on the 50Hz band with the same four codes on the 178Hz band
  Other carrier frequencies which may be used as alternatives are 75Hz and 83,3Hz.
The B.A.c.c. system may also be used to verify the state of the joints: if one of them is broken, the signal is turned red by the system in the rear of the section concerned.


CLD (Local Points Command) allows electric transition of the points, in absence of the corresponding relays interlocking. Besides, it allows the control of normal or reverse points.
It is used especially in the installation and in the calibration of the points before the relays interlocking installation.
CLD is an easy device but with a great reliability and usefulness, thanks to the absence of delicate components like relays. One of the advantages is the settlement and the enhancement of the points transition, allowing to not postponing this phase during the delicate phase of the relays interlocking activation. CLD is also used in the maintenance of IS devices.
CLD is equipped with a lever with electromagnet for the transition, with two keys (a normal one and a reverse one) and with four indicator lights. The functioning is very simple:
  • for the transition, besides the necessary voltage for the power supply of the electromagnet and of the points, both the keys have to be insert in the device
  • the lever has to be positioned on the intermediate position; the electromagnet will be powered, allowing to positioning the lever on the second intermediate position
  • during this passage, the jerkily reverser commands the points transition
  • the electromagnet is powered and the lever can reach the new position
  • after tests on new positioning, the corresponding key can be extracted to obtain the warranty of concordance between the position of the points, the lever and the key


The equipment in use for the Italian Railways ensure the continuity of the feedback circuit of the locomotives direct current. The inductive connections provide a low resistance to the flow of the traction direct current. In the meanwhile, they provides an high impedance to alternate encoded current which is necessary to detect the presence of the train on the track. The inductive connections consist of two windings of copper coils, insert in a sealed container suitable to be placed near the track joint, and encased in special resin able to guarantee its integrity over time.
  • Inductive Connection 500 A
  • Dimensions
  • Width: 648 mm
  • Height: 373 mm
  • Depth: 387 mm
Dimensioni utili interne
  • Larghezza: 1635 mm
  • Altezza: 2200 mm


Direction command and cancellation on railway and metro railway. Release of routes blocked by direction commands.
  • Layout simplification of the control desk, saving spaces in comparison with the traditional solution with mechanical devices (fig.2)
  • Employment flexibility typical of the digital and configurable devices that besides the base functions (command, cancellation, routes release button) can manage optional functions (global commands, command inhibition according to client’s needs)
  • Ergonomics and simplicity, proved by a long test period of Traffic Line Manager activities
  • Installation and maintenance simplification, that, thanks to serial connections, reduce connection conductors number between the subsystems and between them and the devices of the technological room
  • Simple technology (micro relays, PLC, console) facilitating breakdowns search thanks to an easy subsystem substitution
  • Mechanical hardness and electronic reliability which make this devices appropriate to a continuous and prolonged use
The Easy Push-Button Panel has been designed with a distributed architecture and it is composed by two sub-systems:   TRAFFIC OPERATOR INTERFACE (CONSOLE)
The console is designed to be positioned on the control desk of the traffic operator.
The system modular structure allows connecting up to 15 consoles (for huge installation) in parallel, allowing the traffic management by more operators situated in different places or in the same building. Commands are given as in the microprocessors’ systems; clicks are visible on the control display and command activation is done trough a serial network RS485, activating the dedicated command in the correspondent technological room.

The laying method is very flexible: it could be commercial laying (DIN bars) both in F.S. open cabinets or cabinets with electronic equipment. The most popular laying methods are:
  • distributed (different points more close to the devices that have to be commanded with less links)
  • concentrate (unique point with less space waste)
Bi-directional I/O digital modules, exchanging data with the console, allow interfacing analogical output (in this case micro relays) which makes operatives the commands on the corresponding logical circuits. The micro relays used for the command can be allocated on relays retainer plates – F.S. 58 type – (for concentrate laying).


The Unbalance Indicator checks that the components of the 50 Hz (or 83,3 Hz) current in the inductors of the reception induction boxes do not assume an unbalance higher than a fixed value; on the contrary, it forces down the track circuit relays, blocking the corresponding signal. The two currents along the tracks are sensed by two Amperometric Transformers (TA) that convert them into voltage proportional to the currents themselves. In case of perfect balance of the traction currents, in one of the tracks the current associated with the track circuit is summed while in the other track it is subtracted, leading to a situation of unwanted lack of balance. This problem is overcome by the introduction of the Phase Inverter in the transmission system. At every code interval, the Phase Inverter diphase the code current of 180 degrees, making zero the average value read by the Unbalance Indicator (which has longer time constants).
Tension of external power supply:
  • 24 Vcc - 0,25 A
  • 48 Vcc - 1 A
  • 1 LED for input code
  • 1 LED for output code
  • 1 LED 24V power supply
  • 1 LED 4 V power supply
The Unbalance Indicator is composed by the following functional blocks:
  • input band-pass filter which allows only the transit of 50 Hz (or 83,3 Hz) current to the inductive reception boxes’ extremes
  • level comparator of the output current of TA (properly amplified); check that current does not exceed a fixed value, attenuating, if necessary, the output signal which provokes the track circuit relays excitement