CABLEMAX RS-232 LED Link Signal Tester - DB-9 Male to DB-9 Female Connections for Serial Communication Monitoring

Works great for debugging PLC communication issues. I was chasing a ghost issue on an integrated PLC for a stationary battery backup system and this device showed exactly why the issue was happening. My com link cable had a broken wire at one end and this device instantly showed the result of it and finally put the ghost to rest after a quick cable swap.

Handy too. But couldn’t use. Need 25 pin connectors

It does what it says it does and does it well. The LEDs give you a very clear indication of what's going on inside your serial cable. Only caveat is that this is designed to be a pass-through device (one side is male, one female) but both sides have the "female" retention screw holes. This means you can't plug it directly into pretty much anything, because pretty much all computer and even device serial ports also have the female screw holes. If you take the screw holes off with a hex driver, the metal shielding comes with them, so you end up with an unshielded connection. Your choice is either deal with that or get two M->F cables where both ends have the screw threads and put this in the middle. I ended up using a little Krazy Glue to glue the metal shield to the plastic casing, but without the screw holes it's probably not even doing anything anyway. Just a heads up - you may have to do a little hacking, or get extra cables with the correct ends, to get this to attach to anything.

Though devices using serial connectivity are becoming a thing of the past, there are still a good number of devices that are not available with native USB connectivity and require serial port connectivity. Unfortunately, serial devices are not as plug-and-play as USB devices and thus often require some level of troubleshooting to get them up and working. This handy little link tester can be invaluable in determining if the serial connection is mated properly and if communications is occurring. I have used a number of these types of devices over the years and this particular 9-pin device is very convenient. The only drawback is the LEDs are not as bright as I would like to see. If you are in a brightly lit room or out of doors, it may be difficult to see the indication. Overall, I give this tester a thumbs-up.

We were troubleshooting some 232 devices and codes, werent sure if everything was correct (some existing wiring and equipment). Put one of these in line and instantly know weather the wiring is correct or not! Saved lots of time and worked like a champ. You can also see little blinks when data is sent, it is kind of Suttle but there.

This device is perfect. The LEDs are TWO COLOR LEDs, which are lit green for high voltage (not-asserted) and red for low voltage (asserted), so you can tell TX from RX without having to transmit data -- very easy to tell the most common issue which is whether it's a DTE o DCE (and whether you need a null modem or not.) You can immediately see whether modem controls are active, even if they're not being asserted. The only thing that would make this better would be jumper holes and jumper wires, to make a quick fix for two connectors that don't match. But that would make it a breakout box, not just a tester.

Works perfect.

These were once hard to find - glad to have them here at Amazon. There are far too many 25 pin RS-232 testers on the market for a connector that's nearly disappeared. I have one of these in every tool kit and at every desk because they are indispensable for figuring out what's going on when a new piece of equipment wanders into the shop. [Update December 2013] One of the low-star reviews mentioned that these won't connect to chassis mount connectors that have jack sockets. I commented "Easy, unscrew the jack sockets on the tester". I got three new testers today and did that and the metal shells fell off. Older testers had captive metal shells so you could just unscrew the jack sockets if they get in the way. Today's don't. Four 4-40 screws will take care of it holding the shells on, but the product has changed in an unfortunate way.