| 摘要 |
PURPOSE:To secure the visible display in accordance with the types of tones and then to facilitate the operation for calling by giving light emission to the light emitting element with the AC component of the tone. CONSTITUTION:Visible display unit K is inserted in parallel to telephone receiver T into the ordinary telephone set comprising dial mechanism DS, bell B, transmitter microphone T, telephone receiver R and others. Then switch SW of unit K is turned on with receiver R picked up, and thus relay RL turns on switch rl1 and off rl2 each. Then light emission is given to light emitting disde P with the AC component contained in the signal via conductance L and in accordance with the dial tone, the ringing and the busy tone each. Thus the types of tones can be identified by the transmittent state of the light emission without fitting the receiver to the ear. When the called subscriber picks up the handset, relay RL becomes inactive to secure the talking possible state under which switch rl1 turned off and rl2 turned on each. |
