Westermo TF-300 - Manual (Page 2)

2 6606-2201
Modem description
Introduction
TD-300 is an interface converter for connecting terminal equipment to British TelecomÕs
SecureStreamª 300 network. The SecureStreamª 300 network functions as a Virtual
Private Data Network using proven digital technology of British TelcomÕs UK National
Telex network at a data rate of 300 bit/sec. The service offers a transparent connection
between customer terminals. The SecureStreamª 300 is available anywhere in the UK.
The DTE connection on TD-300 can handle either RS-232 or RS-422/485 (one at a
time). It is possible to communicate with different data rates on the DTE (300, 1 200,
2 400 or 9 600 bit/sec) and the line connection (300 bit/sec) due to the fact that the inter-
face converter includes a microprocessor and data buffers.
TD-300 supports three types of connections via the SecureStreamª 300 network:
¥ Fixed Point to Point connection
¥ Fixed Destination Call (Hot Line)
¥ Variable Destination Call
The unit can be configured to different running conditions via DIP switches.
Fixed Point To Point connection
A Fixed Point To Point connection implies that the TD-300 units establishes
a permanent connection via the SecureStreamª 300 network. This also implies that one
of the TD-300 units is the master unit which will establish the condition to the other
TD-300 unit which is set in slave mode.
In this running mode:
¥ The interface converters initiate a call at power up. Retries will be made
until a connection is established.
¥ The connection will not be cleared unless there is a failure.
¥ One modem (the originating modem) must be configured as ÓFixed masterÓ
and the other modem (the answering modem) must be configured as ÓFixed slaveÓ.
¥ DCD is activated as long as a connection is maintained.
¥ CTS is activated as long as a connection is maintained and the buffers
are not filled up (<80% of maximum buffer).
¥ DSR is always activated.