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D
Reserved for selected applications, such as emergency and elevator telephones. When the receiver is lifted, the call is
automatically placed to a predetermined destination. Class D phones can receive calls only within MIT. Not available for
digital phones.
E
Generally reserved for computer dial-up applications. Restricted to placing and receiving calls only within MIT. No access
to toll operators or tie lines.
F
Generally reserved for lobby phones. Restricted to placing and receiving calls only within MIT. Access to toll operators and
tie lines is allowed
Information Services and Technology | 617.253.1101
Ask the Help Desk or contact the IS&T Webmasters.
5ESS Digital (ISDN) Telephone User Guide | IS&T
https://ist.mit.edu/services/telephony/isdnguide
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