Tandem's 
  
                          Written By Forest Ranger 
                                                                              
        The Tandem: 
        ---------- 
  
  
   Each tandem is a line with the capability of signaling any other tandem in 
any other toll switching office in North America. Tandems are programmed to  
route themselves to other tandems if all other direct routes are busy. If all 
other tandems are busy in one area then your tandem will route itself to the 
next nearest tandem that may be in another part of the continent. 
  
   When a tandem is idle waiting for someone to use it sits there whistling 
2600 Cycles per second facing all of thm numbers serviced by that exchange. 
This just means that the tandem is ready to be used. The other side of the 
the tandem is whistling 2600 cycles per second also into a number of trunk 
lines telling the phone system that the tandem has no outgoing or incoming 
calls.  
  
     Dialing the Tandem: 
     ------------------ 
  
  
    You are automatically hooked into a tandem when you dial a long-distance 
phone number. The tandem then sends the number you dialed to the side facing 
away from you. The senling side stops whistling the 2600 cycles per second 
into the trunk line and at this point has been taken over. It will then carry 
the number dialed that will be converted to multi-frequency beep tones to a 
tandem in the NPA and centeral office you requested. 




FROM TARAN KING AT METAL SHOP (314)432-0756