sentences:  The replacement machines will produce paper tickets with no magnetic stripe; instead they will carry a bar code which can be read by some National Rail ticket barriers.As they are not compatible with barriers on the London Underground they will not be accepted for cross-London services on the Underground even if this would normally be included in the fare.A pilot scheme will operate on Cardiff local services from mid-January, however, the tickets issued will not be valid on services operated by other companies, including other Arriva franchises.