| 摘要 |
PURPOSE:To secure an assured detection of the busy state by using a specified bit for the display bit showing that the circuit is in use among the plural bits which are used for the data transfer between the master unit and each slave unit. CONSTITUTION:When no interphone station is in use, transistor TR1 is turned off with busy-state indicating lamp 34 switched off. And when either one of input switches SWa-SWn which select the slave unit is pressed, the transmission data is sent 30 and 7 to the master unit as the monitor signal in the form of ''1XXX'' (XXX: value displaying operating input state of SWa-SWn) and via encoder 29, logic circuit 24 and D-type FF38 each. When the talking is over between the selected interphone stations, reset button 38 is operated. And the transmission data in the form of the monitor signal to be sent to the master unit is turned into ''0XXX''. After this, OUT4-OUT1 of circuit 24 turns to ''0XXX'' when the monitor data processed by the master unit is returned. Thus lamp 34 is switched off. |
