carrying out the final tests on the pager transmitter before it is connected to a nurse call system. This control panel is downstairs; It uses the old RS232 serial interface so I have to make up some custom cables to route this signal through the CAT6 network cabling through the building and connect to the pager transmitter and antenna which is upstairs (as radio transmitting equipment should always go as high up as you can safely put it).
These are test cables using CW1109 jumper wire; eventually I will put one D-sub (the DE9 male which is basically an extension from the panel RS232 out) in a good solid box on the wall near the structured cabling point (there is already a sign warning people not to disconnect it and plug in laptops/PCs as that won’t work and might blow up the network port in the device, RS232 voltages are much stronger). There were two other cables to make – a null modem so I can monitor what is going down the serial port with a PC (a straight through won’t work; as both are DTE) and a DE9 female to DB25 female which can either connect a PC or the signal from the control panel to the pager transmitter. There wasn’t any “plug and play” serial kit like USB until the late 1990s/early 2000s!
But this old stuff works – I’ve got the panel comms running down 38m of twisted pair cable and those test cables aren’t even shielded; in a building with TN-C-S mains wiring (which radiates interference) the whole lot is controlling a radio transmitter with 2 watts ERP (20 times stronger than a DECT phone) and none of the messages are garbled raaa
test with a PC to the pager transmitter (most of the messages from the nurse call system aren’t very interesting other than exit alarms and if I set those off I have to warn the nurses first and cancel them quickly so don’t have time to take photos)
For some reason I thought it a good idea to listen to this whilst making the cable (I know it should have been a DB25 one for historical accuracy but I’d already made that test cable; plus it was a reused connector so didn’t look as pretty).
I probably should use the ventilator fan when making up cables using leaded solder; apparently one sign of lead poisoning is odd behaviour…
Got this in live testing now (the nurses are impressed with it; as they no longer have to walk round the building to look at the nearest display panel, as there are no overdoor lights on this installation)
This is a better constructed RS232 cable, they have to be hand soldered which I haven’t done for about 15 years
the other two test cables will go back in my tool pouch, they (and RS232) are still useful in the 21st century especially for this “Internet of Things” type stuff (which is nothing new; other than the “Internet” side of it).
A final test message before the pager TX is reconnected to the output of the nurse call panel (if anyones monitoring this on a scanner they are unfortunately going to be dissapointed as from now on its only going to be sending the standard messages)
