the switch sw2 is depressed at step 122 the next message and the corresponding control code b if any is retrieved step 126 it is understood that the depression of sw2 at step 122 serves to cancel the message display prohibition and simultaneously retrieve the next message in this particular embodiment steps 124 126 following this the routine goes back to step 116 in the case of a negative output at step 120 the subscriber depresses the switch sw3 step 128 for retrieving the next message stored step 126 if the answer is 34 no 34 at step 116 the routine goes to step 130 fig7 b wherein the message retrieved at step 114 is displayed in the event that the subscriber wishes to prohibit the display of the message now demonstrated on the display 26 he or she depresses the switch sw2 steps 132 134 thus the control code b is written into a predetermined memory location for prohibiting the display of the message presently on the display step 136 as in the above mentioned case the depression of sw2 at step 134 prohibits the message display end simultaneously retrieves the next message steps 136 138 subsequently the routine goes back to step 116 on the other hand if the subscriber does not wish the display prohibition of the message demonstrated steps 130 132 the subscriber depresses the switch sw3 at step 140 and thus the controller 20 retrieves the next message at step 138 and then the routine returns to step 116 after setting the display prohibition or permission of the message s stored an the ram 30 if the subscriber wishes to display the message s the subscriber depresses the switch sw1 for selecting a message display.