now , an embodiment of a radio communication apparatus according to the present invention will be described in detail with reference to the appended drawings . first , fig1 is a schematic system block diagram of the radio transmitter - receiver in fig6 , described before . as shown in fig6 , the microphone 2 is connected to the main unit 1 through a microphone jack . in addition , connectors for connecting antennas 3 and 4 that are selected according to a frequency band , a connector for connecting keys ( keys ), an input / output connector for data ( data ), and a connector for connecting a loudspeaker 5 are disposed on the rear and side surfaces of the main unit 1 . fig1 schematically shows the radio transmitter - receiver including these components . referring to fig1 , reference numeral 51 denotes an input switching circuit for performing switching between a key input and a microphone input . reference numeral 52 denotes a transmitting circuit including functional modules for transmission , such as a modulator , a bpf , a mixer , an exciting amplifier , and a power amplifier , reference numeral 53 denotes an antenna switching circuit for switching uses of the antennas 3 and 4 . reference numeral 54 denotes a receiving circuit including functional modules for reception , such as a high - frequency amplifier , a mixer , a bpf , an if amplifier , a demodulator , and a low - frequency amplifier . reference numeral 55 denotes a frequency synthesizer for supplying a signal of a local oscillation frequency to each of the mixers , modulators , and demodulators in the transmitting circuit 52 and the receiving circuit 54 to make frequency settings and perform modulation . reference numeral 56 denotes an mcu ( micro controller unit ) for controlling functional modules in the transmitting and receiving circuits and an entire system including operation and display circuits , which will be described later . reference numeral 57 denotes a rom that stores various control programs to be performed by the mcu 56 and necessary , fixed data . reference numeral 58 denotes a ram for storing updated data . reference numeral 59 denotes an operator section on which the switches and knobs 11 to 27 are mounted , reference numeral 21 denotes an indicator lamp , and reference numeral 40 denotes a liquid crystal display section . the mcu 56 receives an operation command input signal from the switches and knobs 11 to 27 on the operator section 59 and the switches 28 to 33 contained in the microphone 2 through the input / output interface ( i / f ) 60 . the mcu 56 controls the indicator lamp 21 and transfers display data to the liquid crystal display section 40 through the i / f 60 . accordingly , the basic circuit structure of the radio transmitter - receiver described above is not so different from a normal radio transmitter - receiver . however , this embodiment is characterized in that control programs in “ a status registration mode ” and a “ status confirmation mode ”, associated with functional settings for the system are stored in the rom 57 , and that a data table used for executing these control programs is stored in the ram 58 . next , operation procedures in the above - mentioned modes will be described with reference to the data table and flowcharts illustrated in fig2 to fig5 , one after another . first , the flowchart in fig2 shows the operation procedure in the status registration mode . if an operator turns on the func switch 18 and the lock switch 27 or 30 simultaneously during the operation of the system in step s 1 , the mcu 56 detects the operation command input through the i / f 60 . then , the mcu 56 sets the status registration mode by an interrupt and executes the control program associated with this mode in step s 2 . for the operation of the system , the mcu 56 controls various functional modules in the transmitting circuit 52 and the receiving circuit 54 , the local oscillation frequencies from the frequency synthesizer 55 , and the connection statuses of the input switching circuit 51 and the antenna switching circuit 53 , according to operation command inputs from the switches and knobs 11 to 27 on the operator section 59 and the switches 28 to 33 in the microphone 2 . the mcu 56 thereby makes various functional settings corresponding to transmitting and receiving conditions that have been commanded and selected . if the status registration mode described above is set , the mcu 56 detects functional setting data at that point , and writes it in the data table in the ram 58 in step s 3 . namely , as shown in fig3 , the data table in the ram 58 is configured such that two data cells dset and dref are provided , corresponding to respective functional items associated with the transmitting and receiving conditions . in this status registration mode , the mcu 56 writes functional setting data in the data cell dset in the data table . the functional items in the table are associated with the transmitting and receiving conditions that are modified and set according to the types of the operation of the radio transmitter - receiver . in this embodiment , a mode ( radio mode ), a freq ( t ) ( transmitting frequency ), freq ( r )( receiving frequency ), a vfo / mr ( vfo scanning function / memory channel scanning function ), a step ( frequency adjustment step ), a dsp ( selection of the dsp nr / dsp auto notch / dsp bpf mode ), an af vol ( received sound volume ), an sql ( squelch on / of ), rf gain ( receiving circuit gain ), a clar ( clarifier on / off ), an if shift ( shift function on / off ) are provided as the functional items . if the functional setting data is already written in the data cell dset , it is updated by overwriting . then , if the data writing is completed in step s 4 , the mcu 56 cancels the status registration mode . then , the system returns to its original state in step s 5 . in other words , this status registration mode is set for the occasion of the change of operator , and is used to record the transmitting and receiving conditions at the point of operator change in the data table . after the operator change , an operator who performs communication thereafter may modify the transmitting and receiving conditions or set new transmitting and receiving conditions by means of the operator section 59 and the switches 28 to 33 in the microphone 2 . thus , when the initial operator has returned for the change to resume communication , functional settings associated with the original transmitting and receiving conditions would not always remain the same . in this case , the initial operator turns on the func switch 18 and the home switch 26 simultaneously to set the status confirmation mode . in this case , it should be arranged that the status registration mode is set by the initial operator alone for the occasion when the change to the initial operator is made . an operation procedure in this status confirmation mode is shown in a flowchart in fig4 . according to the mode setting operation , the mcu 56 interrupts the procedure of the system to execute the control program in the status confirmation mode in steps s 11 and s 12 . for execution of the control program , the mcu 56 first detects all functional setting data at that point , as in the status registration mode , and then writes them in the dref ( refer to fig3 ) in the data table in the ram 58 in step s 13 . if the data is already written in the dref of the data table , it is updated by overwriting . thus , the functional setting data for the occasion of the future change to the initial operator is stored in the dset of the data table , while the functional setting data at the current point of the operator is stored in the dref , both corresponding to respective functional items . then , upon completion of data writing into the dref of the data table in step s 14 , the mcu 56 makes comparisons between the functional setting data in the dset and the functional setting data in the dref , for respective functional items , to determine whether all pairs of functional setting data in the dset and the dref coincide in steps s 15 and s 16 . if all pairs of the functional setting data in the dset and the dref are determined to coincide , the status confirmation mode is terminated in steps s 16 and s 23 . if a functional item is detected for which functional setting data in the dset does not coincide with the corresponding one in the dref , the mcu 56 supplies a control signal to the indicator lamp 21 through the i / f 60 to cause the indicator lamp 21 to flash in steps s 16 and s 17 . accordingly , if the indicator lamp 21 does not flash , the initial operator can confirm that the operator who has performed communication thereafter did not modify the original functional settings . for this reason , he can confirm that communication can be resumed with the original functional settings remain unmodified . on the other hand , if the indicator lamp 21 flashes , it means that one or more of the functional settings has been modified . however , it cannot be known what functional setting associated with which functional item has been modified . thus , in this embodiment , the mcu 56 reads out a functional item and functional setting data associated with the functional item in the dset and the dref that do not coincide , from the data table in the ram 58 . then , the mcu 56 transfers them to the liquid crystal section 40 through the i / f 60 for display in step s 18 . to take an example , if functional setting data in the dset in the status registration mode and functional setting data in the dref in the status confirmation mode are as shown in fig3 , it means that functional items indicated by arrows have been modified . consequently , display of freq ( t ): 144 . 86 mhz → 145 . 53 mhz , freqr : 144 . 86 mhz → 144 . 94 mhz , af vol : 32 . 05 db → 48 . 74 db , clar : off → on , and if shift : on → off is performed . since the liquid crystal display section 40 does not have so large a display area , the up and down switches 19 are employed for scrolling so as to allow confirmation of all functional item data that has been modified . next , the operator , who has confirmed from the liquid crystal display section 40 that modification of functional settings has been made , turns on the home switch 26 in step s 19 , if it is necessary to restore the current functional settings to their original states . in this case , the mcu 56 regards a signal indicating turning on of the home switch 26 in the state confirmation mode as a command for restoration . then , according to the displayed functional setting data in the dset associated with the functional items , the mcu 56 controls the functional modules of the transmitting circuit 52 and the receiving circuit 54 associated with the functional items . then , the mcu 56 thereby automatically restores the current functional settings to their original states in step s 20 . if communication is then resumed in the restored original states , the operator should turn on the func switch 18 and the home switch 26 simultaneously in step 21 , as in the case where the state confirmation mode has been set . if communication is to be carried on in the state where modification of the functional settings was performed , the operator should turn on the func switch 18 without turning on the home switch 26 . in response to the operation command signal , the mcu 56 turns off the indicator lamp 21 and then cancels the status confirmation mode in steps s 22 and s 23 . thus , according to the status confirmation mode , when the operator resumes communication , it can be checked from the state of the indicator lamp 21 whether the current functional settings are modified from the functional settings previously stored in the status registration mode . further , if modification has been performed , it can be confirmed which functional item is modified . then , restoration to the original functional settings can be performed by a simple operation , if necessary . incidentally , the status registration mode in fig2 described above is set as required , for the occasion of the operator change , for example . the status registration mode is not effective in the case the immediately preceding functional settings are to be restored after an unintended erroneous operation has been performed . in other words , even if the operator who has changed performs modification of functional settings associated with transmitting and receiving conditions at will , restoration to the state at the point of the operator change alone can be performed . restoration of functional settings to their preceding state immediately before the occurrence of an unintended erroneous operation is not guaranteed . in order to address this problem , use of a periodically automatic registration process in combination with the state confirmation mode as shown in a flowchart in fig5 , in place of the state registration mode set by manipulating the func and lock switches , is effective . first , when the radio transmitter - receiver system is powered up , the mcu 56 activates a built - in timer 56 a in step s 31 . then , the mcu 56 monitors whether an operation command signal has been detected from the operator section 59 or the switches 28 to 33 in the microphone 2 through the i / f 60 in step s 32 . if the operation command signal has been detected , the mcu 56 resets the timer 56 a in steps s 32 , s 33 , and then s 32 . if a predetermined time such as five seconds has elapsed with no operation command signal detected in step s 34 , the mcu 56 writes functional setting data at that point into the dset in the data table of the ram 58 in step s 35 , as in the case of the status registration mode . in this case , except in the initial state , data is already written . thus , in order to update the data , overwriting is performed . then , upon completion of data writing in step s 36 , the mcu 56 resets the timer 56 a in step s 33 . thereafter , the mcu 56 repeats the operations of steps s 32 to s 36 for execution of operations in steps s 33 and s 32 . accordingly , if the before - mentioned status confirmation mode in fig4 is set immediately after the occurrence of an unintended erroneous operation , the contents of the unintended erroneous operation can be confirmed , and functional settings can be returned to the state immediately before the unintended erroneous operation has been performed . thus , communication can be continued smoothly without interruption . incidentally , when the periodically automatic registration process is selectively set in combination with the status registration mode described above , combinations of various switches which are not used by the system , may be allocated to issue a command for the selection . then , either one of the periodically automatic registration process and the status registration mode should be executed , as required . in the above embodiment , the description was directed to the radio transmitter - receiver . the present invention , however , can be applied to transmitters and receivers separately as well . further , in this embodiment , if modification of any of functional settings has been identified in the status confirmation mode , notification is made by flashing of the indicator lamp 21 . notification by a beep sound or display of a message on the liquid crystal display section 40 , for example , may also employed . still further , in this embodiment , the status registration mode and the status confirmation mode are set by the use of combinations of the switches . a dedicated switch , however , may be provided and may also be employed for making a setting operation . those skilled in the art will recognize further variations are possible within the scope claimed below .