Survey Solutions uses device tracking mechanism where for each interviewer account there is an indication of the currently linked device. In short this means that at any moment any interviewer may be utilizing only one device for data collection. Re-linking of the devices is possible, but it has some important consequences (explained here). 

At the same time it is still possible for multiple interviewers to use the same tablet for data collection, but every interviewer must have a different user account in the Android operating system to permit this. If this is not done, once the first interviewer initializes the connection, his name will be fixed in Survey Solutions, and other interviewers will not be able to log in. Refer to the Android OS documentation for supporting multiple users on the same tablet.

When logging in under a different account on the same tablet, the second interviewer will have an opportunity to enter his login/password and connect to the server without a conflict with the first interviewer.

WARNING: if an interviewer starts working under one account and later creates a different account on the tablet and still tries to login with the same credentials, this would be equivalent to switching to a new device (re-linking) and will provoke the re-linking warning with the same consequences (described here). Hence it is important that the interviewer continues to use the same (Android OS) user account for logging in to Survey Solutions.