Can I safely connect my SXV autoguider port to my scope?
The SXV output will drive any standard active-low guider input via an RJ11 ‘telephone’ lead. The SXV output is the same as that in the STAR2000 module and uses 4 opto-isolators for a fully isolated output. This means that you can connect it to any mount without a risk of damage being caused by ‘common’ earth circuits etc. and the circuit is ‘self limiting’ at a few milliamps. The downside is that the polarity of the switches is fixed as positive supply current sinks (ON to guide) and they cannot sink more than a few milliamps. The ‘ON’ offset voltage is also about 1 volt, so some TTL inputs might not switch reliably. All of these issues can be removed by adding a relay box to the SXV output, but most mounts will work without this.
