Because RFL™ and Hubbell® have a policy of continuous product improvement, we reserve the right to change designs and specifications without notice.
RFL VF-5C RFL Electronics Inc.
October 8, 2012 28 (973)
334-3100
E&M Signaling
The VF-5C supports four types of E&M Signaling as shown in Figure 15: Type I, Type II, Type III and
Type V. The E&M signaling jumpers are set according to the type of E&M signaling being used. Refer
to the bottom of page 20 in Table 1 for information on how to set these jumpers.
Type I. Type I signaling is a two-wire scheme, normally encountered in electromechanical switching
systems. The trunk circuit M lead provides the ground (on hook) and the battery –48V (off hook)
toward the model VF-5C module. The signaling from the VF-5C to the trunk circuit is on the E lead
with open circuit (on hook) and ground (off hook).
Type II. Type II signaling is a four-wire scheme, normally encountered in electronic switching
systems. An on hook (idle) condition is indicated by open circuits on both E and M leads and a closure
for off-hook (busy).
Type III. Type III signaling is a partially looped four-wire scheme. It provides better protection against
interference, and is used with electronic switching systems. An on hook (idle) condition is indicated by
an open circuit on the E lead and ground on the M lead. Signaling over the M lead is the same as type I,
except that battery and ground for M lead signaling are provided to the trunk circuit over the MB and
EB leads. A distinction of the Type III interface is that three conductors are used for M lead signaling.
Type V. Type V signaling is a two-wire scheme normally encountered outside North America. The
trunk circuit M lead provides the ground (off-hook), and an open (on-hook) toward the VF-5C module.
The signaling from the VF-5C to the trunk circuit is on the E lead with open circuit (on-hook) and
ground (off-hook).
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