Internal Telephone Modem 3 (ITM3)
Elster’s ITM3 provides modem communication capabilities to
the ALPHA Plus® and A3 ALPHA® meters. The ITM3 has outage
reporting capabilities, intrusion detection, and off-hook
detection. The ITM3 option board is compatible with wide
voltage range ALPHA Plus meters Release 2.7 or later. A3
ALPHA meters require Release 3.0 or later to support the ITM3
option board.
Intrusion and Off-hook Detection
Intrusion detection recognizes when another telephone
extension sharing the telephone line is attempting a call while
the modem is off-hook. When the modem detects another
extension is attempting a call, the modem ceases
communication and immediately disconnects allowing the other
extension to use the line.
The ITM3 option board also provides off-hook detection. Offhook detection recognizes that the telephone line is in use
before the modem attempts a call. When it detects that the
telephone line is already in use, the modem will follow the
user-configured retry strategy to retry the call.
Meters with RS-485 only
Master
RS-485 loop
O
E
N
Modem
[ITM3 & RS-485]
Figure 1. Line sharing enabled
Dual Remote Port Access
On the A3 ALPHA meter only, the ITM3 may be used to enable
dual, simultaneous remote port access to the meter (see Figure
2). To enable, simply install the ITM3 plus a second
communication option board (that is, RS-232 or RS-485) under
the cover of the A3 ALPHA meter. You will be able to
simultaneously access the meter over both communication
links. This provides an economic solution for applications
where a second party desires direct access to the meter (for
example, end customer access, power grid management, etc.).
Outage Reporting
When equipped with an optional outage reporting battery, the
ITM3 option board can report power outages that meets userspecificed criteria. ALPHA Plus meter outage reporting calls are
made using the Elster Electricity protocol; A3 ALPHA meter
outage reporting calls are made using ANSI C12.21 and C12.19.
Line Sharing
By using the ITM3 in association with Elster’s RS-485 option
board, up to 31 meters may share the same telephone line with
no external equipment to install or maintain (see Figure 1). In
this application, the master meter is equipped with both an
ITM3 and an RS-485 option board. Every other meter is
equipped with only an RS-485 option board. All meters can be
read by making a single telephone call. The ITM3 will support
line sharing on both the ALPHA Plus and A3 ALPHA meter.
O
P
E
N
Port 1
Telephone
Port 2
RS-485 or RS-232
Simultaneous
communications
Figure 2. Dual remote port access (A3 ALPHA meter only)
Extended Memory for A3 ALPHA Meters
A3 ALPHA Meters
When used on an A3 ALPHA meter, the ITM3 option board may
be optionally provided with 1 MB of extended memory for
additional interval data recording. This memory, when
requested, is provided directly on the ITM3 circuit board.
The A3 ALPHA meter builds upon the strengths of existing
ALPHA meter designs. Like its predecessors, the A3 ALPHA
meter users Elster Electricity’s patented digital measurement
techniques that offer high accuracy, repeatability, and low
ownership costs. In support of open architecture standards, the
A3 ALPHA meter is the first Elster meter with full ANSI C12.18,
C12.19, and C12.21 support.
ALPHA Plus Meter
The ALPHA Plus solid-state polyphase meter is a powerful
meter that builds on the patented ALPHA metering technology.
The ALPHA Plus meter can be a single phase, 240-volt, one-rate
demand meter or a polyphase, wide voltage supply, multi-rate,
real/reactive meter that validates meter service connections
automatically, performs power quality monitoring, and provides
load profile reading with remote communications.
Any ALPHA Plus meter can be upgraded to any other
configuration through option boards and reprogramming
techniques. The ALPHA Plus meter is designed so that one
meter can be applied at all line voltages ranging from 96 to 528
volts. The wide voltage range also eliminates the need for some
commonly used ANSI wiring forms without the need to rewire
existing sockets.
The ITM3 option board requires wide voltage range ALPHA
Plus meters release 2.7 or later.
The A3 ALPHA meter supplies many standard features such as
the following:
•
•
•
•
self reads (up to 15 self reads may be stored)
over 50 different instrumentation display quantities
system service checking
Class 0.2 accuracy for transformer rated and self-contained
meters
The ITM3 option board requires A3 ALPHA meters release 3.0
or later.
Technical Specifications
ITM3 Option Board
Optional outage reporting
battery operational life
Communication rate
S-base
1200 bps or 2400 bps
A-base
6.95
[177]
1.35
[34]
6.95
[177]
Over 100 outage reporting calls in a ten-year period
7.6
[193]
10.3
[262]
6.4
[162]
6.4
[162]
9.4
[238]
5.5
[139]
0.75
[19]
LINE
Dimensions in inches [millimeters]. For reference only. Do not use in
construction.
LOAD
2.56
[65]
2.5
[62]
Elster
Raleigh, North Carolina, USA
+1 800 338 5251 (US toll free)
+1 905 634 4895 (Canada)
support@us.elster.com
www.elster.com
© 2005 by Elster. All rights reserved. Information herein is subject to change without
notice. Product specifications cited are those in effect at the time of publication.
Printed in the United States. Rev. A. July 2007.