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S1-4: DSR Normal during Local Loopback – DSR ON during Local Loopback. When
enabled, this strap forces the DSR lead ON during a Local Loopback. This allows DTEs
that rely on DSR being on to send test messages to the DSU.
When disabled, DSR is turned Off during a Local Loopback.
S1-5: Elastic Store – When enabled, the DSU compensates for small (3 bits) timing
phase drifts that may occur when the DTE interface of the DSU is connected to the DTE
interface of an analog modem to provide an extended network. If you do not have an
extended network, place the strap in the disable position.
S1-6: Remote Digital Loopback Enable – When enabled, the DSU responds to a front
panel-initiated Remote Loopback request from a remote DSU. When disabled, the DSU
ignores the Remote Loopback request.
NOTE:
For nondiagnostic data over a multipoint network, set this strap on only one
tributary DSU.
S2-1– S2-4: Data Rate – The DSU has ten data rate selections. Refer to Table 3.
S2-5: Streaming – This strap is provided at a tributary DSU to detect when the terminal
is streaming (that is, the RTS circuit from the DTE remains on longer than the streaming
terminal timer). This selection is only effective when the DSU is strapped for switched
RTS operation. Streaming detection will not be performed if the DSU is in a test
condition.
The DSU activates the streaming timer whenever the customer Request-to-Send (RTS)
circuit turns ON, and it declares the streaming condition if the circuit is still ON at the
end of the timer interval. If the circuit is turned Off before the end of the interval, the
timer is reset. The timeout is fixed at 27 seconds for subrate speeds of 19.2 and below,
and at 3 seconds for 38.4, 56, and 64 kbps.
S2-6: System Status – When enabled, the DSU turns off the DTE Data-Set-Ready
(DSR) interface lead when the network sends the Out-of-Service or Out-of-Frame
message, or no signal is received from the network. When disabled, a network alarm
has no affect on DSR.
S3-1: Faceplate Disable – This strap controls the LL, TP, DL, and RL test switches on
the DSU's front panel. When Switch S3-1 is open, the front panel switches are disabled
and the DSU will not respond to any faceplate test requests. When S3-1 is closed, the
faceplate switches are enabled. Depending on how this strap is set, the DSU will or will
not respond when these switches are pressed. This selection is designed to prevent
accidental disruption of data transfer.
S3-2: Continuous/Switched Request-to-Send – When enabled (continuous), the
DSU holds its internal RTS circuit ON independent of the DTE RTS interface lead.
When disabled (switched), the DSU internal RTS circuit follows the DTE RTS interface
lead.
S3-3: Local Loopback (LL) through EIA-232-D Connector – When enabled, this
strap permits the use of Pin 18 of the EIA-232-D interface to initiate a Local Loopback.
S3-4: Local Loopback (LL) through CCITT V.35 Connector – When enabled, this
strap permits the use of Pin LL of the V.35 interface to initiate a Local Loopback.
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