Transferring files

Null Modem to Xfer Files

If you have ever had the need (or desire) to connect your Kaypro to another Kaypro (or another computer) to transfer files and you don't have a modem, here is a scheme to connect two together which makes each think it is using a modem. You will also be able to transfer data at much higher rates than the standard 300 or 1200 baud that most modems afford.

If you have an existing RS-232 cable that you don't need for another purpose (I got mine at a swap-fest), make the following changes with a small (20-25 watt soldering iron.

ON ONE END OF THE CABLE ONLY, unsolder the wires from pins 2 and 3, then reverse these two and re-solder them. Unsolder the wires from pins 5 and 8, then reverse these two and re-solder them. Unsolder the wires from pins 6 and 20, then reverse these two and re-solder them. ON BOTH ENDS OF THE CABLE, unsolder the wire from pin 4 and fold it back so it will be out of the way. Don't cut the wire, so you can return the cable to its original configuration should you ever desire. Then solder a small bare piece of solid copper wire lying across pins 4 and 5, forming a jumper between the two. Check all connections to insure that you made each change correctly, then reassemble the hoods on the 08-25 connectors.

If you don't already have an RS-232 cable which you can modify, you can make one up from a length of (at least) nine conductor cable and two DB-25 connectors. Follow the wiring diagram below, noting that pins 4 and 5 at each end of the cables are jumpered together.

NULLMODEM

DB-25 connector	cable	DB-25 connector
PROT GND	1------1	PROT GND
XMTD DATA	2------3	RCVD DATA
RCVD DATA	3------2	XMTD DATA
REQ TO SEND	4-+
CLEAR TO SEND	5-+----8	RCVD LN SIG DET
DATASET RDY	6---20	DATA TERM RDY
SIGNAL GROUND	7----7	SIGNAL GROUND
RCVD LN SIG DET	8--+-5	CLEAR TO SEND
	+-4	REQ TO SEND
DATA TERM RDY	20---6	DATA SET RDY