AUTHORIZED SURFACE NODE
=======================

The door beyond the machine room has no hinges. It opens inward anyway.
Beyond it is a control passage made from black material, with old
telephone wire suspended inside like fossils.

The key projects no light, but every relay on the service level turns
toward it. A status strip reads:

    MAINTENANCE SIGNAL: INBOUND ONLY
    RETURN LINE: NOMINAL

Then, beneath it:

    VOICE DETECTED BELOW CARRIER

The word VOICE is crossed out and replaced with SOURCE.