Telog Data Download Cable

The standard C-21ATC cable inter-connections between a PC and a Telog Linecorder.

Enhanced Version

Some Com port drivers will not allow any communications through the com port until the control lines are brought high. USB to RS232 convertors are unusually sensitive to this. The normal solution is to bridge pins 1, 4, & 6, and 7 & 8 in two separate groups, as shown in this version of the cable. Please note: You cannot plug a USB-RS232 adapter straight into the Linecorder as the pin conversion is still required.

Marc's version of a C-21ATC cable

Some drivers will not bring the RTS high without active CTS, DSR & DCD signals. In the final version of the cable, a pair of diodes are used allowing either the RTS or DTR to supply the required signals. Those unfamiliar with RS232 communications may wish to refer to this web-page on PC RS232 ports.

In most cases, dispensing with the resistors and connecting Pin 5 of the PC directly to Pin 7 of the Telog will work. However, it has been known for many notebooks to not have Pin 5 (signal ground) connected. R1 and R2 provide an "alternative ground" arrangement for this situation yet limit any ground loop currents that may exist should both Pin 5 and the case be connected within the PC. A full explanation regarding this can be found here.

R1, R2	-    10 to 22 ohms, ¼watt resistor.
D1, D2	-    1N4148, or other suitable signal diode.
P1	-    DB9 female connector
P2	-    DB9 male connector

If there are any questions please email me

Note: This web page does not form part of any official documentation.
Any information contained herein is used at own risk.
The information provided here is used at your own risk.

©  M.T.P. - 08.04.04