Motorola 68230 - Vanguard 300 DSU/CSU Operator's Manual page 69

DSU Reporting
Introduction
CTP reporting of information differs for the DSU daughtercard in terms of input
signaling. Use the CTP "Monitor" function from the Main menu to view these
signals.
Note: "L" stands for "Signal Low" and "H" is "Signal High".
Differences in CTP Reporting of Input Signals
Input Signal
NIS (Not In Service)
BPV (Bipolar Violation)
DL (DSU Loopback)
C+ (Positive Sealing Current)
C- (Negative Sealing Current)
CTP reporting of information for the DSU differs in terms of output signaling.
Although these output signals are not directly accessible to the user, the DSU
option software manipulates these signals and may be useful for informational
purposes.
Function
Normally "L." Used to determine if the other
end of the connection is available. If no signal is
received, the DSU option is in DSU loopback
mode, Or If idle codes are received, NIS is "H."
An "L" means the DSU option has received a
bipolar violation. An "H" is expected during
normal operation. Expected to toggle during a
DSU loopback condition.
Normally "H." An "L" indicates entry into a
DSU loopback mode.
"H" if the DC current on the telephone company
interface is not in the positive direction. If both
C+ and C- are "H", no sealing current exists,
which often occurs when connected to other
DSU type hardware. C+ would be expected to
be "L" normally when connected to central
office equipment (OCU) hardware.
"H" if the DC current on the telephone company
interface is not in the negative direction. If both
C+ and C- are "H", no sealing current exists,
which often occurs when connected to other
DSU type hardware. C+ would be expected to
be "L" normally when connected to central
office equipment (OCU) hardware.