Phone in use indicator 5

     >>-----------------+------+---->> phone line 
                        |      | 
                        |      o 
                        |       / 
                        |      /   momentary switch 
                        |      | 
                        |      / 
                        |      \   1200 Ohm 
                        |      / 
                      -----____| 
                       / \ 
                      /___\  SCR 
                        | 
                        / 
                        \  600 Ohm 
                        / 
                        |     ^^ 
                      -----  // 
                       / \  // 
                      /___\    LED 
                        | 
                        | 
     >>-----------------+--------->> phone line 

Sources

• Terri Barber barber[at]beowulf.ucsd.edu

Category:Telephone