Cabletron Systems 1800 manual Figure C-9 E&M Signaling Types

Tie Line

P BX Equipment

V

E

V M V

	Type I
P BX	Tie Line
	E q u ip m e n t
V	E
	S G
	M
	SB	V
		V
	Type III

P BX	Tie Line
	E q u ip m e n t
V	E
	SG
	M	V
	Type V

PBX	Tie Line
	Equipment
	E
	SG
	M
	SB	V
	Type II
PBX	Tie Line
	Equipment
	E
	SG
	M	V
	SB
	Type IV

Figure C-9 E&M Signaling Types

The illustrations in this figure are abstracted from the specifications to show the essential components of the signaling circuitry. In this figure, the symbol V refers to battery voltage, which can be -25 Vdc to -65 Vdc, and is usually (nominally) -48 Vdc. Each of the illustrations in the figure show the PBX's E&M interface on the left, and the corresponding tie line equipment interface on the right.

Type I

With the Type I interface the tie line equipment generates the "E" signal to the PBX by grounding the "E" lead. The PBX detects the "E" signal by sensing the increase in current through a resistive load (this is indicated in the figure by the unconnected node branching from the right side of the "E" resistor). Similarly, the PBX generates the "M" signal by sourcing a current to the tie line equipment, which detects it via a resistive load. The Type I interface requires that the PBX and tie line equipment share a common signaling ground reference. This can be achieved by connecting signal ground from the PBX to the SG lead (pin 8) of the RJ45 connector.

Voice Configuration Reference Information C-15