Instrument ID Switch Codes

Scope
This document defines the instrument ID switch encoding scheme used by the instrument change and interlock systems to detect and identify instruments on the SDSS 2.5-meter telescope.

Instrument ID Switches

Instruments installed on the instrument rotator will be identified by decoding a series of microswitches located near each of the three instrument kinematic mounts.  There will be one switch bank at each kinematic mount location;  each switch bank will contain four normally-closed (NC) microswitches.  NC switches are used in order to provide active-high signals to the interlock system.   Low signals from all switches on a given switch bank will indicate a disconnected cable.  High signals from all switches will indicate that the system is functioning but that no instrument is in place on the rotator.  A mismatch between the patterns from the three switch banks will indicate a fault condition, such as a broken wire or faulty switch in a given switch bank.

The following table lists the switch actuator output patterns for the instrument ID switches.  The actuators will be mounted on the instruments;  the switch banks will be mounted on the instrument rotator.