[ntp:questions] Convert PPS signal from BNC to RS-232!

Jonathan Buzzard jonathan at uk.me.buzzard
Tue Mar 6 22:16:36 UTC 2007

On Mon, 05 Mar 2007 16:03:41 +0000, David L. Mills wrote:

> Hal,
> The orignal Bell 103/201/202 modem specification required a bipolar data 
> signal +-6V or more. Later, the 113 modem specification allowed unipolar 
> signals, but was not widely adopted. In some cases the modem or UART 
> chip does work with TTL signals, but not all. It takes two transistors 
> and a resistor to fix that, or better yet a MAX232 chip. Details are in 
> the NTP documentation on the gadget box page.

Around 99.9% of all RS232 interfaces on a PC will detect a zero as a
voltage below somewhere in the region of 1-2V and a one as anything above
that. If it where not so my receiver would not work, but it does



Jonathan A. Buzzard                 Email: jonathan (at) buzzard.me.uk
Northumberland, United Kingdom.       Tel: +44 1661-832195

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