Hi all, A customer has a problem with an old CNC Mill that uses an LSI11 for control. There is an DEC VT510 connected to the LSI11 as console, The LSI11 is booting from an RX01 (2?) and uses some basic programm.. pretty much a museum... The problem is, that on the Sigma Systems serial Card (similar to the M8043) the AM26LS32 receiver is going bad afer some on/off cycles of the computer. I've already fitted a socket for the 26LS32.. The AM26LS23 only could tolerate +-7V common mode voltage difference and seems to be not the best part for RS232.. I've checked the terminal and changed in the meantime the X2 and X capacitors at the line filter, the protective earth from the Line is connected to the Pin 7 (singal Ground) of the DB25 Connectors and I could'nt measure realy potential differences that could be the cause for the damadge of the receiver chip. To make it short..chase away the problem I wan't to use some RS232 Opto Isolator in the RS232 Line. I've got a used BLACK BOX SP340A-R2 and an SP400A-R3 from Ebay, additional some Power Injector from BLACK BOX for powering that with some wall wart that wasn't included. I've now looking for a Manuals for the BACK BOX SP340A and the SP400A to configure the dip switches in there. There are 2 DIP Switches with 8 positions each..for configuring the power supply for the opto couplers from the DB25 connectors it seems. Haven't found anyithing related on bitsavers, there is blackBox in the communication archive, but nothing related to the SP340 oder SP400.. Can anybody help please? Regards, Holm -- Technik Service u. Handel Tiffe, www.tsht.de, Holm Tiffe, Goethestrasse 15, 09569 Oederan, USt-Id: DE253710583 info(a)tsht.de Tel +49 37292 709778 Mobil: 0172 8790 741