In SX Microcontrollers, SX/B Compiler and SX-Key Tool, william wrote:

[b]SX KeyPhone v2.[/b]

Here are the Shematic and PCB files in ExpressPCB format.

There are a lot of changes (improvements) compared to V1.
Some of the major changes are :-

1.  SX52 (EOL'ed) has been replaced with SX48 and SX28.  This is due to more pins required on a "bus" system.
The SX28 now acts as a "bus master", controller deciding which Ext is allowed connect to the bus.
2.  Twin Analog bus design allows 2 pairs of conversation at any one time.
3.  All Mechanical relays (including ring injection) have been replaced with solid state relays for better relaibility and low current consumption, except for 2 relays used for power failure switch-over.
4.  Power Adapter required is now only 12V instead of 24V to save on costs.  ( 12V Adapters are more common and cheaper )
5.  Almost all Gnd and Pwr pins on SX48 are now connected, and closer bypass capacitor added.
6.  Bottom ground plane added under both SXes in hope to improve immunity to external sparks.
7.  Ring signal generation transformer is now placed off-board.
8.  Six twin solid state relay ICs added for bus interfacing.  One op-amp relay removed ( no longer required )
9.  Hybrid Circuits removed.  Board size still about the same.

Good Luck.

---------- End of Message ----------


You can view the post on-line at:
http://forums.parallax.com/forums/default.aspx?f=7&p=1&m=101111#m111636

Need assistance? Send an email to the Forum Administrator at forumadmin@parallax.com

The Parallax Forums are powered by dotNetBB Forums, copyright 2002-2006 (http://www.dotNetBB.com)