MULTISERVER 500
68
The E&M Voice/Fax Interface Card interfaces the
voice/fax section of the Multiserver 500 with the
trunk side of a Private Branch Exchange (PBX) as
shown in Figure C-1. This type of telephone
interface breaks out the audio signal and status
control (or signaling) on separate wires.
Audio is transmitted on either a single pair
(2-wire operation) of wires labeled T/R, or on two
pairs (4-wire operation) of wires labeled T/R and
T1/R1, as configured. When configured for 2-wire
operation, the T/R pair transmits and receives
communications. When configured for 4-wire
operation, the T/R pair transmits and the T1/R1
pair receives.
Signaling consists of an M lead and an E lead. In
the E&M interface module the M lead is defined as
the input or receive lead and the E lead is defined
as the output or transmit lead. In some cases added
return leads termed SB and SG are used.
There are five E&M signaling formats defined:
Types I, II, III, IV, and V. However, only three
formats are in common use today: Types I, II, and V.
Type I is the most common type used in the United
States, while Type V is common throughout the rest
of the world. Type II was designed for compatibility
with some AT&T
®
PBX types.
C.1 Differences Between Models
There are two versions of the E&M Voice/Fax
Interface Card:
•
MX401C—E&M Standard
. This model meets all
North American regulatory-agency safety
requirements. It uses the Type I signaling
convention.
•
MX402C—E&M Enhanced
. This model meets
all European and North American regulatory-
agency safety requirements. You may strap it
one of three ways to match the signaling
convention of the interfacing PBX equipment:
Type I, II, or V.
Unless specified otherwise, information in this
appendix applies to both models.
Appendix C:
E&M Voice/Fax Interface Module
Figure C-1. Connections for the E&M Voice/Fax Interface Module.
MULTISERVER 500
Station
Side
Trunk
Side
PBX
E
M
T
R
T1
R1
E
M
T
R
T1
R1
E&M
Interface
Module
