5.8.7 Intercommunication systems. Intercommunication systems installed
within LEAs present audio security hazards similar to those related to
telephone systems. Unless necessary for efficient operation,
intercommunication systems should not be installed in LEAS. The design of
many intercommunication systems allows audio in the vicinity of any station
to be intercepted at any point along the connecting cable run. The speakers
in public address systems may also function as microphonic transmitters. If
determined to be essential, all components of the system, including
connection cables, should remain within the established secure perimeter.
Under no circumstances should intercommunication systems that use ac power
lines or rf energy as the transmission medium be used. Intercommunication
systems must be tested to ensure the components do not generate rf emissions
which may be intercepted and exploited.
5.8.8 Specialized telephone equipment. The installation of specialized
telephone equipment, such as telephone answering devices and speaker phones,
is discouraged within LEAS. Such systems add to system complexity and
increase the potential for undetected exploitation. In cases where
operational need overrides the security ramifications, specialized telephone
equipment should be installed using the provisions of paragraph 5.8.3.
5.8.9 Approved equipment. With the rapidly changing technology in the
telephone industry, the designer should consult DIAM 50-3, the local
cognizant TEMPEST authority, or the cognizant security authority for current
approved telephone equipment and procedures.