therefore prevent uncoupling. A relatively lightweight spring is enough to maintain the wedge position in the event of a loss of compressed air to the deploy side of the actuator (also known as the wedge-engine). Uncoupling is achieved by air directed to the retract side of the wedge-engines on both couplers to retract the wedges and free the hooks; uncoupling is completed by simply moving the vehicles apart. In the event of a loss of retract air, the wedges can be moved manually to allow uncoupling. Schwab coupler The , made by Schwab Verkehrstechnik AG, Schaffhausen, is used on Stadler Kiss and SZU Be 510. It has been offered in four versions: Schwab coupler (FK-15-12) for standard gauge trainsets can be found on "Stadler GTW" and "Stadler FLIRT" trainsets of the SBB (GTW and FLIRT), Thurbo (GTW), BLS (GTW), (FLIRT) and SOB (FLIRT). Schwab coupler (FK-9-6) for tram and metro trains, among other things Schwab coupler (FK-5.5-4 and FK-3-2.5) for narrow gauge railcars Schwab coupler (FK-15-10) for standard gauge multiple units are compatible with Scharfenberg type 10 The Schwab coupler is superior in many ways to many other automatic couplers because it makes the pneumatic and electrical connections automatically and is capable of automatic uncoupling. it is used primarily in Switzerland in regional rail passenger transport. Wabtec is working on an automatic coupler based on Schwab, a possible replacement of the buffers and chain coupling on European railways. Shibata coupler The Shibata coupler is a variation of the Scharfenberg coupler which was developed by Japanese Government Railways (JGR) engineer in the 1930s for electric trains. It is the standard coupler type for all passenger trains in Japan as well as on commuter and subway trains in South Korea. Shinkansen (bullet train) rolling stock utilize a variation of the Shibata coupler developed by Sumitomo Metal Industries in the 1960s which uses rotary tight-lock pins, and which coincidentally bears a closer resemblance to the Scharfenberg coupler rather than the Shibata coupler. Dual couplings and match wagons Sometimes a wagon with one coupling system needs to be coupled to wagons with another coupling type This may be needed when taking metro rolling stock from its manufacturer to the city where it is to be used. There are two solutions: use a barrier vehicle(s) which has different couplings at either end. use a coupling adaptor. use a match wagon which has the same dual