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Connector pin usage in different cases
The below diagrams depict the pins of a USB-C socket in different usage cases.

USB 2.0/1.1
A simple USB 2.0/1.1 device mates with one pair of D+/D- pins. Hence it does not require any connection management circuitry and therefore is backward compatible with even the oldest USB devices. VBUS and GND provide 5V up to 500mA of power.

USB Power Delivery
USB Power Delivery uses one of CC1, CC2 pins for power negotiation up to 20V 5A (or whatever less the source can provide). It is transparent to any data transmission mode and therefore can be used together with any of them.

USB 3.0/3.1/3.2
In the USB 3.0/3.1/3.2 mode two or four high speed links are used in TX/RX pairs to provide 5 to 20 Gbps throughput. One of the CC pins is used to negotiate the mode. VBUS and GND provide 5V up to 900mA, in accordance to USB 3.0 specification.

Alternate Mode
In the Alternate Mode one up to four high speed links are used in whatever direction is needed. SBU1, SBU2 provide an additional lower speed link. If two high speed links remain unused, then a USB 3.0/3.1 link can be established concurrently to the Alternate Mode. One of the CC pins is used to perform all the negotiation. Also an additional low band bidirectional channel (other than SBU) may share that CC pin. USB 2.0 is also available through D+/D- pins. The available power may be 5V up to 500mA by default, 5V up to 900mA if USB 3.0/3.1 link is active or whatever the Power Delivery is providing.







Automatic semaphores
Automatic semaphores are used on lines equipped with automatic block signaling. Their colour language is the same as aspects S1-S5 of semi-automatic semaphores. The main difference regards S1 (red) signal - it can be passed with maximum speed of 20 km/h after full stop.

Automatic semaphores have their posts painted white (without red strips) to be easily distinguished apart from semi-automatic semaphores.

Warning shields
Warning shield (Pol. tarcza ostrzegawcza) is distant-only signal display. It is used on lines not equipped with ABS. Placed in the braking distance allow driver to stop before the semaphore they regard. Their colour language is the same as semaphore aspects S2-S5, making them technically a semaphore which is just incapable to display S1 (stop) aspect.

Their posts are painted grey and equipped with the warning shield sign.

Semaphore repeaters
When the semaphore aspect is not visible from the proper distance (because of track curves for instance), a semaphore repeater is installed to aid drivers. Up to three repeaters may be installed if needed. A semaphore repeater is not a substitute for a warning shield. Their posts are painted grey and equipped with plates with Roman numerals: III, II, I where the "I" stands closest to the semaphore. Their color language is identical to warning shields, except the fact they also have continuously glowing white light, which informs that this is not a valid signal but a repeater.

The following table presents as example, a station-entry semaphore designated "B" displaying the aspect S13 (speed limit 40 km/h, stop at the next semaphore) preceded with warning shield and three repeaters:

Level crossing warning shields
Level crossing warning shield is placed in a braking distance before an automatic level crossing. The signal tells the driver whether automobile drivers are warned against a train (blinking red lights, barriers). Normally, level crossing warning shields display no signal (are dark). They light up in the front of an approaching train which is the first clue that the system is working correctly.

Level crossing warning shields signals are unrelated to other signals, therefore in case of Osp1 signal a train must proceed at 20 km/h regardless the higher speed allowed by last semaphore.

Their posts are painted black and white strips.

Maneuver shields
Maneuver shield (Pol. tarcza manewrowa) is shunting signal, used exclusively on stations. A consist shunting on such signals must not leave the station. Maneuver shields are either stand-alone or incorporated into semi-automatic semaphores, which bear letter "m" on such occasion.

Stand-alone maneuver shields have their posts painted gray.

Mechanical signals
Category:Railway signalling by country Kolejowe sygnały świetlne