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A rollsign, roll sign, bus blind, or destination blind is a mechanical display used to indicate the destination. They are commonly seen in older city buses, streetcars and subway cars. As a part of the contract, they are standard on London bus routes. Modern equipment substitutes a digital display in place of a rollsign, but the long life of these vehicles ensures that many systems continue to use these devices.
Names of the route or destination are printed on a long sheet of reinforced paper or Tyvek. The long sheet is rolled onto the top roller and attached to the bottom roller. Similar to a cassette tape being played. There is a gap between the rollers, large enough to display a complete name, and a strip light fitted behind the blind as to illuminate it at night. When the names need to change, the driver/operator/conductor simply turns a handle which engages one roller to gather up the blind and disengages the other, until the desired blind display is found.
Electronically controlled ways now exist to changing the blinds. These are standard on so-called bendy buses or Citaro Gs. This is controlled by a computer through an interface in the driver's cabin. On the reverse of the blind there are barcodes printed so the computer winds the blind and a reader reads the barcodes until the requested display is found. The on-board computer is normally programmed with what order the displays are and can be programmed using the non-volatile memory should the blind be changed. These blind systems are normally accurate, however over time the blind becomes dirty and the computer may not be able to read the blind so leading to incorrect displays. For buses such as bendy buses this disadvantage is outweighed by the need (compared to manual) to change each destination separately, if changing route this could be up to seven different blinds.
Heavy grade linen was the favourite material but in the 1940s, London Transport started producing blinds that were made by sticking paper slips onto a linen backing. This method had the advantage that large numbers of destinations that were in use on a number of blinds e.g. "KINGS CROSS" or "TRAFALGAR SQUARE" could be screen printed and held pending demand. As time passed the blind department in Chiswick gave way to cost cutting and now all LTs blinds are produced by McKenna Brothers from Cheshire. They use a computerised system of printing the blinds directly onto tyvek, a type of fibrous paper material that has extremely resilient qualities. They were produced for operators all over the UK and use the distinctive London Transport-designed Johnson typeface which is similar to Gill Sans but with minor variations. This typeface has been in use for almost 70 years.
The old style linen blinds are quite collectable and high prices can be found at eBay auctions and transport sales.