by the second key engages a locking mechanism preventing operation of the cylinder lock application_number US 87415078 A description a cylinder lock 1 is mounted in the wall 2 of a door hood or the like of a motor vehicle not shown in detail and comprises a housing 3 and a closing cylinder 4 arranged rotatably therein a catch 5 is connected with the closing cylinder 4 which operatively cooperates with a locking mechanism not shown in detail further an electric contact device 6 is provided on the cylinder lock 1 by which the electric alarm and or electromagnetic locking devices 7 8 may be switched on or off fig2 and 4 a safety key 9 serves for the common operation of the closing cylinder 4 and the contact device 6 on the other hand with a further operating key 10 only the closing cylinder can be operated according to fig3 the contact device 6 is constructively combined with lock 1 inside the closing cylinder 4 tumblers 13 14 are arranged in double rows 11 12 and are supported upon spring elements 15 16 and engage into grooves 17 18 of housing 3 when neither of the keys 9 10 is inserted into the housing 3 if a safety key 9 corresponding to.