Carrier Access SNMP manual Detector-Driver Functions, 48V

4-Wire E&M/TO Configuration

interface incorporates a signaling current detector (the “ear” listening to the line). The multiplexed or carrier channel equipment always originates signaling on the E-lead coming from the transmission line. The signaling current detector is found on the M-lead going toward the transmission line.

The 4-wire E&M/TO voice card can be optioned to operate either as channel equipment or switching equipment. Since the Access Bank II - SNMP typically operates as a voice and data multiplexer, the card is usually configured as channel equipment. This is referred to as tandem operation because the card operates in tandem (i.e. back-to-back) with another transmission device.

Table 11-1lists the generic functions performed by the Detector/Detector Return and Driver/Driver Return when the 4-wire E&M card is configured to operate as Channel Equipment or Switching Equipment.

Table 11-1: Detector-Driver Functions

Channel Equipment	Detector is on M-lead function
	Driver is on E-lead function
Switching Equipment	Detector is the E-lead function
	Driver is the M-lead function

-48V

-48V		E-Lead
		Detector
	Tandem Mode
	(Originating)
	(Switching Equipment)

M

E

E&M Type 1

M-Lead

Detector

Normal Mode

(Terminating)

(Channel Equipment)

Figure 11-3: E&M Signaling Type 1

11-4 9/24/01