Thank you again. Your negative result is a little surprising. If the 0119CF command is failing then perhaps the frequency check is off. You can see if the transmission light frequency counter is running using: DEVELOPERPW 36OD If this is running then you can compare the frequency to the upper and lower limits which are in the data store, see the output of '1422OD' and check m_fUpperFrequencyLimit and m_fLowerFrequencyLimit. If the counter is not running then it would seem your DTP41 is not compatible with your DTP41T base. It would be nice to know how the pulses are generated. Seems that pulses are passed in pin 3, must be an oscillator in the base? Also it would be interesting to know if the base has a light sensor or is it sensing the current or a voltage. Douglas On Wed, Sep 2, 2009 at 2:40 PM, Graeme Gill <graeme@xxxxxxxxxxxxx> wrote: > Doug Private wrote: > >> Hello Graeme, >> >> Thank you for giving this a try. The firmware appears to be the same in >> both models, >> and the hardware does appear to be the same, so there would appear to be a >> good chance. >> > > I'm not so sure. > > If you could help just a little more it would be appreciated. I am not >> sure >> if the problem >> I see is the third input pin or a setting in the unit. >> > > Doubtful, as I said, even with the genuine base, it doesn't work. > The base has two settings, black or white/transmission. > With it set to white/transmission, it fails. > > If you could try the >> following it may >> help narrow it down. >> >> Command '0119CF' - transmission measurement mode. >> Does this fail for you with error 3F or succeed? >> The light comes on and it may be probing pin 3. >> > > It returns an error BF/3F, DTP41_TRAN_LAMP_ERROR > > If you try 0119CF on the DTP41T with the base switched to black does it >> still work? This would narrow down if the unit is probing pin 3, the >> light >> channel, or an internal setting. >> > > It doesn't work in either position. > > With the DTP41T instrument, 0119CF returns 00, > so the instruments are not identical. > > Graeme Gill. > >