|   Technical Information in PDF   |  
  |   Installation and  Operating  Instructions   |     |    Installation and Operating   |  
  |    |  Installation and Operating |  
  |    |  Installation and Operating |  
  |    |  Installation and Operating |  
  |    |  Panel Template |  
  |    |  Installation |  
  |    |  Operating |  
  |    |  
   Radio Specific  Installation  Instructions  Figure 4 installation drawing modification for specified radios.     |     |     |     |     |  
  |    |    SPA-400 For ICOM A3, A6 , A22, A24 Radios    |    SPA-400 For King KA 134 Audio Panel    |    SPA-400 For King KMA 20 Audio Panel    |  
  |    |     |     |    SPA-400 For U-174 / U Headset Jacks    |  
   |  
  |   Modification   |     |    It allows pilot and co-pilot to transmit and receive on the aircraft radio and intercom between themselves, while back passengers can have a separate conversation without interrupting the front two.   |  
  |    |  Panel Mount Intercom Transmit Sidetone Modification Circuit Board 1528, (SPA-400 S/N 6069006 to Current & SPA-600 S/N 1102528 to Current) |  
  |    |    Panel Mount Intercom Transmit Sidetone Modification Circuit Board 1440, (SPA-400 S/N 6053486 to 6069005 & SPA-600 S/N 1101839 to 1102527)   |  
  |    |    Panel Mount Intercom Transmit Sidetone Modification Circuit Board 1092-4, SPA-400 Panel Mount, S/N 61960 to 6053485   |  
  |    |    Panel Mount Intercom Transmit Sidetone Modification Circuit Board 1092-3, SPA-400 Panel Mount, S/N 60975 to 61959   |  
  |    |    Panel Mount Intercom Transmit Sidetone Modification Circuit Board 1092-2, SPA-400 Panel Mount, S/N 60500 to 60974   |  
  |    |    Panel Mount Intercom Transmit Sidetone Modification Circuit Board 1092, SPA-400 Panel Mount, S/N 60001 to 60499.   |  
  |    |    This modification is used when a Sigtronics SPA Intercom is connected to a radio or audio panel that has a low impedance headphone output (less than 100 ohms).   |  
  |    |    Installation Instructions for use on Sigtronics Panel Mount Intercom Systems   |  
  |    |    This modification applies to a Sigtronics SPA-400/600 or ST-400 / ST-600 installations.   |  
  |    |    Add pilot isolate to a SPA-400 / SPA-600 Intercom.   |  
  |    |    Music input options for Sigtronics SPA panel mount intercoms.   |  
   |  
  |   Trouble-shooting   |     |    Instructions designed to assist avionics technicians in diagnosing comm? radio transmit problems following intercom installation.   |  
   |  
  |   Helpful Hints   |     |    Communicating in Unusually High Noise Environments   |