E&M Type I signaling uses two leads, E and M,
which share a common ground path. This signaling type
is commonly used with electromechanical switching
systems. Most electronic systems do not use it due
to the noise induced by the common ground path.
Type II interface is designed for use with electronic
switching systems. It uses four wires, a pair for
the E lead and a pair for the M lead. The signaling
system is fully looped with the CU and SE having independent
batteries and grounds. The SE controls the E lead
and the CU controls the M lead.
E&M Type V interface is widely used outside North
America. It can be used in SSDC5A type circuits on
the IDNX. This interface is an unbalanced version
of E&M Type IV signaling from the trunk circuit
to the signaling facility is over the M lead; signaling
in the reverse direction is over the E lead. Local
ground is used for off-hook instead of the ground
obtained from the SB or SG lead. This makes this interface
a two-wire type
Integrated services digital network, an international
communications standard for sending voice, video,
and data over digital telephone lines or normal telephone
wires. ISDN supports data transfer rates of 64 Kbps
(64,000 bits per second).
Each protocol is parameterized, giving developers
the ability to adapt the protocol to multiple target
environments worldwide. The MFC-R2 protocol states
and events are identical for all countries, but certain
parameters, such as tone duration, vary.