Instruction manual

FUNCTIONAL DESCRIPTION
switchhook information is also sent over these channels.
The electronic power feed device provides phantomed -48 volt dc power for the MET
terminals over the data channels.
The electronic power feed device is a “smart”
circuit breaker. When it senses an overcurrent condition, it indicates the condition on
an output lead and goes into thermal shutdown if not turned off by the on-board
microprocessor.
When the overcurrent condition disappears, the circuit breaker can
be turned on by the on-board microprocessor.
STARLAN Interface (ZTN84)
The STARLAN Interface (ZTN84) Circuit Pack functions as either a gateway or a bridge
between System 25 and the AT&T STARLAN NETWORK (Release 2 of STARLAN only). The
ZTN84 CP contains much of the circuitry common to the other CPS in the system, that is a
Sanity and Control Interface (SAKI), a Network Processing Element (NPE), and a 8031
microprocessor. The CP also contains the circuitry required to perform the protocol
conversion on the data as it travels from one system to the other. These devices include a
80186 microprocessor, 82586 coprocessor, four Octal Asynchronous Terminal Mode 2 to EIA
Asynchronous LSI (OATMEAL) devices, and a logic sequencer. The 80186, the 82586, and
the logic sequencer (PLS105N) work together to add and delete the protocol used by the
Local Area Network (LAN), while the 80186 and the OATMEALS work together to add and
delete the protocol used by the PBX.
The ZTN84 can support up to four circuit switch connections between the Private Branch
Exchange (PBX) and the Local Area Network (LAN); this capability is provided by the four
OATMEALS and the NPE, the latter being a four channel device. In providing a connection
between the PBX and the LAN, capabilities such as file sharing, printer services, connections
to hosts, and modem pooling may be accessible across systems.
The OATMEAL devices on the ZTN84 are used in such a way as to support asynchronous
data communication at any of the standard rates ranging from 300 bps to 19.2 Kbps. The
asynchronous protocol that is used is a subset of Digital Communications Protocol (DCP)
Mode 2, as only “I” channel information is transmitted, where the data is formatted in High-
Level Data Link Control (HDLC) frames.
The ZTN84 has been designed with a hardware interface that allows the CP to be connected
to a STARLAN NETWORK as an OUT connection.
This can be connected to a STARLAN
NETWORK Extension Unit (NEU) IN connection, in a star configuration.
The design of the ZTN84 is not fully compatible with the daisy-chain arrangement of the
STARLAN NETWORK, since much of the daisy-chain circuitry was left off of the card. For
testing purposes, the card can be used in a limited daisy-chain arrangement, where the
ZTN84 is connected to a personal computer (PC) that possesses a Network Access Unit
(NAU). The ZTN84 and the PC should be the only two devices forming the LAN. The daisy-
chain circuitry was omitted in order to reduce cost and save board space. It is also the
architectural design of the system that the PBX be connected to the LAN by a NEU. The NEU
can either be local, in the telephone room with the switch, or in a remote office.
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