| 摘要 |
PURPOSE:To apply backup function to as many push bells as possible by producing a signal for identifying the first or second push bell when either of them is operated and producing a signal for identifying the first push bell by operation of the second bell when a switching bell is operated. CONSTITUTION:When each of push bells 27 to 29 is depressed, a signal corresponding to it is read out as it is by a control section 25 if a switching bell 31 is not depressed in an operation section 26. When the switching bell 31 is depressed, a signal corresponding to a stop bell 28 is produced by depressing a reverse bell 29, further signals corresponding to a start bell 27 and the reverse bell 29 are produced, respectively. When the switching bell 31 is depressed, each of the push bells 27 to 29 of a group 30 of push bells in usual use is shifted by one. Thus, even if one push bell is failed when actually used, another push bell can respond to that by depressing the switching bell 31. Therefore, backup function is obtained. |
