the block in question I use is
```
        - host: "services.dnb.de"
          port: 80
          db: "sru/dnb"
          servername: "DNB"
          checked: 0
          rank: 2
          syntax: USMARC
          servertype: sru
          encoding: utf8
          recordtype: biblio
          sru_options: "sru=get,sru_version=1.1,schema=MARC21-xml"
          sru_fields: "title=dnb.tit,isbn=dnb.num,controlnumber=dnb.idn,srchany=dnb.woe,author=dnb.atr,issn=dnb.num,subject=dnb.sw,dewey=dnb.ddc,stdid=dnb.idn"
```