Te l e p h o n e L i n e
RTU Modules
The Telephone RTU system consists of a pair of devices, a transmitter
and a receiver that allow the transmission of 4 analog and 4 digital
signals over a twisted pair or dedicated telephone line. The signals are
encoded and transmitted as a unidirectional FSK signal. The 4 analog
input signals at the transmitter are multiplexed to a single analog output at the receiver. There are 2 selection inputs on the receiver to
determine which signal appears at the output.
The four digital inputs at the transmitter are presented as four digital
outputs on the receiver. There is a fifth digital output which is activated when the communications link is broken.
Both the receiver and the transmitter are housed in a metal enclosure
with a TS35 rail mounting foot. Optional brackets may be installed for
panel mounting. Contact the factory for details.
The Telephone RTU works on any twisted pair (with distance limitations) or any telephone line that is unpowered and has no dial tone. In
Ontario the units were tested on a 9600bps analog line, "Sched 4
Type 4" provided by Bell. This type of line allows almost any transmission distance to be covered since the maximum input to output
loss is guaranteed.
The transmission speed is 600bits per second of FSK encoded data.
Each transmission "package" consists of 16 bytes (of 12 bits length).
The protocol itself has been written specifically for this application.
The units have been designed to meet North American telephone
interface standards and are isolated from the telephone line by 600
ohm transformers.
Connection is achieved through the 6 way RJ11 (telephone) connectors. Irrespective of whether communications is to occur over the telephone line as described above, or a twisted pair only the two middle
pins (pins 3 and 4) are used. Pin 2 of the transmitter is connected to
pin 2 of the receiver. Pin 3 of the transmitter is connected to pin 3 of
the receiver. See figure 1.
United States
Weidmuller Inc.
Weidmuller Ltd.
Weidmuller, S.A. de C.V.
821 Southlake Blvd.
10 Spy Court
5 Sur No. 4311
Richmond, Virginia 23236
Markham, Ontario L3R 5H6
Col. Huexotitla
Telephone: (800) 849-9343
Telephone: (800) 268-4080
72534 Puebla, Pue. Mexico
Facsimile: (804) 379-2593
Facsimile: (905) 475-2798
Telephone: (22) 37 2549
Email: [email protected]
Email: [email protected]
Facsimile: (22) 43 1981
Email: [email protected]
Telephone Line RTU
Figure 1 - Interconnection
Typical transmission medium
twisted pair or analog telephone data line, no dial tone, unpowered (in Ontario this is
9600 bps, "Sched 4 Type 4")
Transmission Speed
600 bps, 16 bytes, 12 bits per byte
Transmission Protocol:
Transmission Interface
600Ω transformer coupled
Communications Failure
Delay of 3 seconds.
Accuracy at 25°C:
0.08% ± 1 bit typical
(based on 0.1% input resistors)
Step Function Response
600-1700ms (typical)
Minimum pulse width (high or low)
300ms (typical)
Maximum Frequency (sine wave)
0.1Hz (typical)
Step Function Response
600-1550ms (typical)
Minimum digital input pulse width (high or low)
450ms (typical)
Maximum Frequency
0.1Hz (typical)
Telephone Line RTU
Transmitter Module
Power Supply Voltage
Supply Current (typical)
120mA @ 15V, 80mA @24V, 75mA @ 30V
Analog Input
4 inputs, resistor selectable 0-20mA (factory setting) or 0-10Vdc
other ranges possible, contact Weidmuller
Analog Input Impedance
(nominal-using recommended values):
0-10Vdc input 20KΩ (use 2 x 10kΩ.1% per channel)
0-20mA input 250Ω (use 1 x 250Ω 0.1% per channel)
±0.1% across temperature range
Digital Input Current
6mA @ 30Vdc supply
5mA @ 24Vdc supply
3mA @ 15Vdc supply
As a result of the low current gold plated contacts should be used, or electronic drivers.
Iin=(V-1.6)/4700 where V is the voltage supplied to the anode of the input opto
(marked Com.An.).
LED Flash rate
250ms on, 250ms off
Operational Temp
-20° to 70°C
Catalog Number
Transmitter Module
991652 0000
Use the following table to determine which resistors to change for a given input configuration. Recommended values are
Rx=Ry=4.99kΩ, 0.1% for 0-10Vdc input or Ry=10Ω, Ry=250Ω ohms, 0.1% for 20mA input. Default is 0-20mA.
Calibration: see Application Notes
Figure 2 - Dimensions
Contact Weidmuller for the “Telephone RTU” Application Guide or
download it from our website
Telephone Line RTU
Receiver Module
Power Supply Voltage
Supply Current (typical)
135mA @ 15V, 120mA @24V, 125mA @ 30V
Analog Output:
Jumper configurable 0-20mA (factory setting) or 0-10Vdc (other ranges possible,
contact Weidmuller). Single output
±0.1% across temperature range
Analog Drive Output:
Voltage output
10mA @ 10V 1000Ω min.
Current output
20mA output <=500Ω over full supply voltage range
RLmax (20mA out)
Digital Input
((50*Vs)-200 where RL is the load in ohms and Vs is the supply voltage.
Analog Channel Selection: SelA, B
Digital Input
2, Optically Isolated
Digital Input Current
6mA @ 30Vdc supply
5mA @ 24Vdc supply
3mA @ 15Vdc supply.
As a result of the low current gold plated contacts should be used, or electronic drivers.
lin=(V-1.6)/4700 where V is the voltage supplied to the anode of the input LED
(marked Com.An.).
Digital Output
Built-in Back EMF diodes for direct relay drive.
Standoff Voltage
Maximum Output Current
Maximum On voltage @ 100mA
1Vdc (typical)
Digital Output
5, Open collector (4 associated with the inputs, 1 for communications failure).
Built-in back EMF diodes for all outputs- commoned at Com.Kt
When an input is active, (current flowing through the LED input) the associated output will be
active (sinking current). When there has been a communications failure, the COMMUNICATION
FAILURE output will go active (sinking current).
LED Flash rate(nominal):
Communications Active 300ms on, 300ms off
Communications Inactive 1.5s on 1.5s off
Operational Temp
Transmitter -10° - 70°C
Catalog Numbers
Receiver Module
991653 0000
There is a single analog output. It may be configured for voltage or current output by setting a jumper. Ranges may be
adjusted away from 0-20mA (factory setting) and 0-10V, see Application Note "Telephone RTU" for details.
For convenience, Channel 1 is presented when the channel selection is disconnected.
Calibration: see Application Notes
Specifications subject to change without notice. 99990203- 06/2001 Printed in Canada