> >AFAICT the hardware manual has the polarity of /RING0 wrong
>
> It should be active low, so that the RS-232 RI line pulses positive
> when a call is received.  It's a good line to connect to an /INT pin

As far as I can determine, /RING0, on this unit, is active high. ie it's
normally low and goes high for those conditions you mention. I thought
at first this was due to differences between the TC35 (the actual
cellular engine) and the MC35, which is a TC35+interface, but the
description is in the interface manual, so ???? Anyway, it's hooked
up to INT1 with a rising edge detect and seems to work alright

That's not to say I'm running it on deficient commands that someone
at Siemens will tell me "makes it work upside-down" !!

Cheers for the errors/fixes mentioned. I've a collection of those too.
It's quite disappointing and means silly extra work

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