3Com S26x, S27x DSU Input and Output Signaling, Input Signals, Output Signals, Signal Description

DSU Input and Output Signaling

DSU Input and Output Signaling

Introduction	Input and output signaling information is useful as a debugging tool and replaces the
	EIA summary information associated with other DIM types.
Input Signals
	This table describes the input signals.
	NIS		Not In Service
			This signal is normally low (L). If no signal is received, or the DSU
			option is in DSU Loopback mode, or if idle codes are received, NIS is
			listed as high (H). This signal is used to determine if the other end of the
			connection is available.
	BPV		Bipolar Violation
			This signal is “H” during normal operation. When the signal is “L,” it
			indicates that some type of bipolar violation was received by the DSU
			option. The signal toggles during a DSU loopback condition.
	DL		DSU Loopback
			This signal is normally “H.” An “L” indicates that a DSU loopback
			mode is entered.
	C+		Positive Sealing Current*
			This signal is “H” if the DC current on the telephone company interface
			is not in the positive direction.
	C-		Negative Sealing Current*
			This signal is “H” if the DC current on the telephone company interface
			is not in the negative direction. An “L” indicates that the DSU option
			has detected a negative “sealing” current and is therefore performing a
			CSU loopback.
		Note
		When both C+ and C- are “H”, it indicates that no sealing current exists. This is
		often the case when connected to other DSU type hardware. Normally, the signal
		for C+ is “L” when connected to central office equipment (OCU hardware).
Output Signals
	Although you cannot directly access the output signals, they are manipulated by the
	DSU option software and may be useful for informational purposes. The following
	table describes the output signals.
		Signal	Description
	RS		Reset
			This output resets the DSU option hardware. Its normal operating state
			is “H”.
	LL		Local Loopback
			When this signal is “L”, the DSU hardware is locally looping data back
			to the PathBuilder S24x, 26x, and 27x switch hardware by way of the
			EIM.

3-8 PathBuilder S24x, 26x, and 27x Switch Hardware Installation