The problems recently have been because of the 405575 cascade line. When the Residencia reclaimed the numbers for the houses they gave us the numbers 840,841,842 and 843 cascaded on 575. These lines have been very unsatifactory and seem to suffer from poor line quality causing the modems to hang up requiring either a line reset or modem reset or both
As a temporary measure one of the two remaining modems on 575 has been transfered to a dedicated line of 636 and seems stable.
In Santa Cruz experiments are in progress to connect modems directly to the sparcs to give an extended range of services and reliability. When this service is available it will be made public.
This text in http://ing.iac.es/~cfgdb/notes/ directory tree.