1 Providers of the public telephony service which generate connections must ensure that at least one number in conformity with the Swiss E.164 numbering plan is transmitted as the telephone number of the calling line.
2 They must transmit the number that is allocated to the customer for the service within the framework of which the connection is established. The other telecommunications service providers involved in the connection shall not modify transmitted numbers.
3 Providers of the public telephony service may enable their customers to transmit other numbers when the connection is established, provided they can demonstrate a right of use. If providers are aware that customers are transmitting numbers for which they do not have a right of use, they must take appropriate measures to prevent the transmission of these numbers.
3bis If customers provide prima facie evidence that unauthorised third parties are using their numbers, the providers of a public telephony service may with the consent of the customers concerned block calls that transmit the relevant numbers. The foregoing does not apply to calls that are actually made from the connections of the customers concerned.43
4 Transmitted numbers must be provided with an identifier which indicates whether they are based on information from the calling customer or on information from the provider generating the connection, and whether the latter has verified the customer's number information.
5 No numbers from the ranges 0900, 0901 or 0906 shall be transmitted as numbers of calling lines.