Hi Erik,
I have read the postings between you and Russell Bull.

I have something to say in this regard:

1. I knew that RS485 is 1 pair, but I typed it as 4 wire RS485. Now I am confused, what to call a device that has 75176 (2 nos). and having 4 wires for communication between a PC and multiple MCU-51 devices which can transmit information in both the direction (obviously in Half Duplex Mode). Here in Mumbai,India, our and many of our compititors are specifying (and it is a general term) as 4-wire RS485.

1a. There is another misconcept here in India. If you are aware of the DIN Standard of the boxes used for Temperature controller, Timers,Counters,etc.
As per the International standard, DIN size is 192x192(mm), Half DIN size is 96x192, Quarter DIN as 96x96. But here, people (and manufacturers of these instruments) specify that DIN size is 96x96, Half DIN is 96x48, and Quarter DIN is 48x48. I do not know who,how and when this has started. But for the last 12 years these are specified and nobody has any misunderstanding about it.

2. I had written an awfully long post to explain the flaw in Microsft Windows98 about Sleep(100), so I mistakingly wrote 4-wire RS485. But the meaning behind that statement (to Andy Curda) was whether he is using 2 wires or 4 wires for communication. I think that should ease off the tension between you and Russell.

3. I am also having some Proximity readers (made in Taiwan). And have used many of them and they have worked sucessfully well. No problems whatso ever. The trickiest part with them is that their specification says that they are RS232 compatible. But if you measure the voltage on their TxD pin, it is always 0Vdc. You connect them to the PC Serial Port and after swiping the card, they give the perfect data without any problem, even in programs like HyperTerminal. I have measured the voltage(TxD) on the CRO, they give 5 Vdc pulses.

I was just wondering what version of RS232 Standard are they complying to? Because, as far as my memory goes there is no such RS232 device (or RS232 standard) that gives or specifies 0Vdc in idle condition and 5Vdc pules (measured on CRO), during data transfer.
But these devices have been working in the field without any problem since more than a year.

I am expecting your comment on this, Erik.

With warm regards from,

Mr. Kiran V. Sutar.