Some very old Dialogic telephony cards (the ancient D/41-B for instance) use 6,053 Hz and 8,117 Hz sample frequencies. Newer cards use exactly 6,000 Hz and 8,000 Hz. Vox Studio can accommodate both types. You cannot buy the old cards anymore but they still are installed in systems in the field, so you need to know about this requirement.
The difference is not noticeable when playing back speech files from one type of card to another. However, when precisely pitched tones (DTMF for instance) are recorded, the difference may be significant. Check with your telephony card vendor for the exact sample rate of the card(s) you are using. Some telephony cards can play back at several programmable rates. In that case, check with your software vendor to select the exact sampling rate and file format that your applications need.
Remember that some telephony applications and cards need files sampled at 6 KHz, others at 8 KHz and even others at 7.2 KHz! Check with both your card vendor and the vendor of your application software platform.