RFL SMX3 / 21
Page 3 of 22
Issue 1.4
User Manual
08 June 2009
1. Introduction
Prompted by SP Powersystems’ operational requirements in the former MANWEB
region, RFL developed a four channel sub-multiplexer to support operation of their
MPR – LZPK102 protection relays and SCADA systems over leased digital circuits.
The requirements for this multiplexer is described in SMX3/40 Sub-MUX X.21 High
speed sub-rate multiplexer User Manual Release 2.01.
This new Dual-Protocol version, SMX3/21, is designed to support protection relays
with an X.21 serial interface rather than a V.24 interface, together with two V.24
channels (typically used for RS232) that can be used for the existing SCADA
equipment.
2. Features
The RFL SMX3/21 Sub-MUX is a hardened (EATS 48-5) sub-rate multiplexer. The
equipment is 19” rack mountable, 1U high, with reversible mounting brackets
permitting either the connectors or the LEDs to face the front of the rack.
SMX3/21 aggregates one X.21 data channel (Channel A) and two V.24 data
channels (Channel B & Channel C) across a single point to point X.21 service. Data
Channel A is permanently allocated to Aggregate Channel 1. The V.24 Data
Channels B and C may both be assigned to either Aggregate Channel 2 or
Aggregate Channel 3. Both V.24 channels may be assigned to a single aggregate
channel; this feature is useful for supporting SCADA systems where multiple
terminals are attached.
LEDs are provided for Power Supply healthy and for the status of all ports. Two volt
free alarm changeover contacts are provided for Power and Aggregate
Communications healthy.
BT KiloStream or similar
Port
assignment
& sharing
X.21
Port
V24
Channel B
Optional Aggregate Concatenation
SMX3 / 21
Block Diagram
Ch. A
Port
X.21
Conc
at.
Port
X.21 Channel A
Ch. B
Port
V24
Ch. C
Port
V24
V24
Channel C
MUX
Agg.Channel 1
A
gg.Channel 2
A
gg.Channel 3
