ETS/EN 300 396 defines the Terrestrial Trunked Radio (TETRA) Direct Mode Operation (DMO). It specifies the basic air interface@ the inter-working between Direct Mode (DM) groups via repeaters@ and inter-working with the TETRA Voice plus Data (V+D) system via gateways. It also specifies the security aspects in TETRA DMO@ and the intrinsic services that are supported in addition to the basic bearer and teleservices. The present document defines TETRA Managed Direct Mode Operation (M-DMO). M-DMO provides a means to restrict the use of Direct Mode Operation (DMO) by requiring prior authorization before a Direct Mode Mobile Station (DM-MS) is permitted to transmit on a radio frequency. This modifies the operation of DM-MSs from that specified in ETS 300 396-3 [3]@ EN 300 396-4 [4]@ ETS 300 396-5 [5] and EN 300 396-7 [7]. M-DMO provides a control mechanism by which radio frequencies (M-DMO frequencies) may be given for DMO use for a period of time; those frequencies are considered to be managed frequencies. All M-DMO devices operating on a managed frequency shall comply with the transmit restrictions defined in the present document. An M-DMO DM-MS (M-DM-MS) may receive the authorization to transmit from a broadcast signal sent on the M-DMO frequency.Or@ alternatively@ ii may obtain the authorization directly on the V+D side from the SwMI or from an M-DMO management station. The authorizing unit which sends the broadcast signal on the M-DMO frequency is referred to as an M-DM-AUTH. It obtains the authorization to operate as an M-DM-AUTH from the V+D SwMI or from a management station that is authorized to allocate frequencies for M-DMO An M-DM-AUTI-T may be a stand-alone unit (performing only the authorization function)@ or it may perform also the function of a DM-REP@ DM-GATE or DM-REP/GATE. The content of the present document is as follows: - Clause 4: provides an overview of M-DMO; - Clause 5: describes the procedures for M-DMO mobile stations; - Clause 6: describes the procedures for M-DM-AUTHs; - Clause 7: describes the operation of M-DMO frequencies; - Clause 8: describes the usage of the authorization presence signal; - Annex A: lists the timers and constants specific to M-DMO; - Annexes B through F: describe the differences from ETS 300 396-3 [3]@ EN 300 396-4 [4]@ ETS 300 396-5 [5] and EN 300 396-7 [7] arising from M-DMO. The present document assumes familiarity with operation of TETRA in a network environment as described in EN 300 392@ and with operation of TETRA in Direct Mode as described in other parts of ETS/EN 300 396. The present document does not define the process for deciding which frequencies and allocated to M-DMO use.