INITIALIZATION PROCEDURE OF THE ATSU ROUTER(continued)SCAN MASK VALIDATIONThe last parameter required is the scan mask validation. The three VHF SCAN SELECT pages give an ordered list of service providers usable for VHF data communications. TEST TLS and TEST HAM are activated only for test and shall not be selected for airline operations. The NEW SCAN SELECT function is used to erase the previous selection. The VHF3 SCAN MASK is compulsory for the router operation.