[GreenKeys] PC Interface to Mod 28 Teletype

[dave sigafoose]

Group,

Ordered a Telebyte 65A - RS232 to Current loop converter last week directly from Telebyte.  Rather expensive at $129. plus shipping, but it arrived in 3 days.

The 65A is full featured with many configuration options.  Only took a few hours to get everything working. 

It comes with an LCD display which gives the status of RTS, CTS, DCD, DTR, DSR, and the TD and RD signals.  This really helps in getting everything hooked up correctly.

1) Used an old model Dell D300 with a DB-9 COM1 port with Windows 98 SE.

2) Connected the Dell to a straight through DB-9 female to DB-25 male cable.
       
3) Used a DB-25 Female/Female adapter as the 65A is DB-25 male.

4) Configured the 65a for DCE as the Dell is DTE. 
 
5) The 65A in active mode can supply DC loop current for both transmit and receive loops in full duplex.  

I chose to configure for half duplex and passive which means that the model 28 internal power supply provides the loop current and that the keyboard and typing unit are on the same loop.

6) Connected the positive voltage loop wire to the K+ terminal and the negative voltage loop wire to the C- terminal.
  
7) Downloaded and installed HeavyMetal. 
 
8) Originally had HeavyMetal configured for 45.5 baud, and it printed garbage.  Once I changed the HeavyMetal configuration for 74 baud, and no local echo, the mod 28 began typing flawlessly. 


If you are looking for a PC to current loop interface, I would highly recommend the 65A.



Dave Sigafoose