ST-15 ARGOS PTT For Use On Walrus

The information below is provided for individuals who are still deploying these older systems. Some of the system information or limitations, information on frequency allocation or usage, and/or comments made on "state of the art" may be time sensitive or even outdated. Please contact Telonics if you have any questions about the information provided on this page.

Telonics has been involved in Walrus research programs for over twenty years. Initial studies involved attachment of small conventional VHF transmitting subsystems to the tusk of Pacific Walrus at Round Island, Alaska. In the 1980's we worked extensively in the development of Argos PTT's for application to both Pacific and Atlantic Walrus. In the early efforts PTT size and durability as well as reliable attachment to the animals tusk was critical to the success of tagging efforts. By the late 1980's PTTs could be made small enough to survive for extended time periods (several months) to the tusk of male Walrus. In the mid 1990's Telonics produced the first GPS/ Argos linked units for Walrus research. These units were deployed by scientist of the USGS on animals at Cape Pierce, Alaska. GPS positions were obtained from animals at sea as well as during haul out periods. To the best of our knowledge this deployment was the first successful use of GPS/Argos linked units on marine mammals. We have been involved in a long history of equipment development for the marine mammal community in general and for the study of this unique species in particular. Note: The configuration listed in this paper is an ARGOS PTT and does not contain a GPS receiver.

TWT-400 ARGOS PTT Configuration

The TWT-400 configuration was designed for attachment to the walrus tusk. The unit is constructed from 1.4 inch thick brass rod and contains two 1 inch indentations to accommodate the banding strap used to attach the unit tothe tusk. Please Fig.1. Typically the tusk is also filed to help prevent the band from sliding down the tusk and being removed. The unit is typically mounted on the tusk such that the antenna is oriented upward toward the face of the walrus. The saltwater switch contacts are located on the same surface as the antenna. The TA-7 antenna is normally provided with this configuration.


Housing Dimensions: 7.8 length x 1.4" outside diameter
Weight: approximately 700 grams.

Operational life assuming 50 second repetition period:
64 days with 100% duty cycle and all time spent on surface
244 days with 25% duty cycle (or approximate time spent on surface)
560 days with 10% duty cycle (or approximate time spent on surface)

ST-15 Core Unit Specifications (for reference)

Argos Type Certification: MODEL CM 10001-004
Weight: 11 g, Electronics Only (For Reference)
Size: 2.5 " (L) X 0.67" (D)
Frequency: 401.650 MHz (In accordance with Argos Specifications)
Operating Temperature Range: OPTION 004, -40° TO +70°C; OPTION 005, -40° TO +60°C.
Storage Temperature Range: -60° TO +80°C.
Humidity: 90% NON-CONDENSING.
Power Output/Peak Current: 500 mw*/385 ma at 7.3 Vdc, 400 mw*/355 ma at 6.0, Vdc, 200 mw*/315 ma at 4.0 Vdc, (50Ω Load Impedance).
Voltage: +4.0 Vdc to 7.2 Vdc.
Quiescent Current: <45 ua (Operating), <5 ua (Shutdown).
Case Polarity: Negative (-) Ground
RF Output Impedance: 50Ω
ON/OFF Switching: A normally open (N.O.) switch turns the PTT on.

Saltwater Switch and Antenna Options

The configurations listed above are typically ordered with a saltwater switch option that assures synchronization of the Argos transmission with surfacing. The switch also suppresses transmissions while the unit is under water, thus saving power and maximizing operational life of the configuration. The power savings associated with the saltwater switch (suppressing transmissions while the animal is under water) is additive to the power savings associated with duty cycling.

Various antenna options are also available to allow the selection of the appropriate antenna material. Any PTT requires an antenna to radiate the signal to the satellite; therefore, appropriate antenna design is critical in successful deployment and function of a PTT subsystem.

TA-7 Helical Transmitting Antenna: This antenna consists of a foreshortened helical antenna 0.25 inches in diameter and 2.25 inches in length. This antenna is provided with the TWT-400 unless otherwise specified by the user at time of order.

TA-11 Internal Transmitting Antenna: This antenna is captivated inside the urethane structure containing the saltwater switch contacts. This internal antenna is the most durable of all options for this configuration. This antenna does not perform as well as the TA-7 antenna however the very low profile of this option is critical in some applications. This antenna is a specialized antenna that should not be ordered without consultation with the factory. Special order required.

ST-15 Walrus Configuration

Software Options

Software choices for the ST-15 PTT for marine applications include:

LO950413 Location Only: Four bytes of zeros.
BM950413 Location & Surface Counter: Thirty-two bits, including 16-bit surface time counter followed by a second 16-bit message which is a repeat of the first message. The value in each counter should be multiplied by 1.024 to convert to number of seconds on the surface. The count is not made over a specified interval but instead increments continuously until it reaches a value of 65535, at which time it rolls over and begins at zero. By comparing count values with the time coding on individual receptions of the PTT, the surface time between receptions can be calculated. Note: If all time is spent on the surface and the saltwater switch is open, the counter will roll over after approximately 18.6 hours.
FS970102 Location and Animal haul out threshold: Four bytes of zeros. In this software, you can use the salt water switch to suppress transmissions when the PTT is under water. Transmissions can also be suppressed when the animal hauls out for a user-determined length of time. You must define the number of seconds (not to exceed 16,383) that the PTT must be out of water before transmissions are stopped. You must also define the number of seconds (not to exceed 255) that the PTT must be under water, once in the haul out mode, before reverting to the standard Argos transmission.
BW970617 Location & Number of time animal surfaces: Thirty-two bits, including 16-bit number of times animal surfaces followed by a second 16-bit message which is a repeat of the first message. The counter records the number of times the animal has surfaced. The counter continually increments until it reaches a maximum value of 65,535 at which time it rolls over and begins again at 0. Only one count is recorded per surfacing. A new surfacing cannot occur until the animal has been submerged for 6 consecutive seconds.

Service Commitment

Since 1970, Telonics has built a reputation based on product quality, product support, service, and customer satisfaction. Telonics strives to produce the highest quality products, and to support those products accordingly.

Because of extreme conditions and the unpredictable nature associated with most telemetry applications, problems occasionally arise. Most problems can be resolved quickly. In all cases, we hope to be able to work in partnership with users to resolve problems to the user's satisfaction and to uphold our demonstrated commitment to excellence. If problems should arise, all products must be returned to our factory for failure analysis.


Telonics warrants its products to be free from defects in material and workmanship for a period of one year from the date acquired. Telonics does not warrant batteries.

If a defect occurs, return the equipment to us within the proper time frame at the following address: TELONICS, 932 E. IMPALA AVENUE, MESA AZ USA 85204-6699. Damage to any equipment resulting from misuse, accidents, unauthorized service, extreme conditions, or other causes, is excluded from this warranty. Telonics does not assume responsibility for loss or damage to equipment during shipment. Telonics does not assume responsibility for delays resulting from shipment on commercial or private carriers. We insure all equipment shipped from our facility and suggest that shipments to Telonics also be insured.

Upon the timely return to our facility, if defective, the product will be replaced or repaired at our discretion at no cost to the customer. This remedy is the exclusive remedy. This product is supplied without any further warranties or conditions, expressed or implied, including warranties of merchantability, quality or fitness for particular reason or those arising by laws, statutes or trade usage or course of dealing.

The entire risk, as to the results and performance of the product, is assumed by the customer. Neither Telonics, nor its suppliers, shall have any liability to the customer or any other person or entity for any indirect, incidental, special, or consequential damage whatsoever, regardless whether Telonics has been told of the possibility of such damages or that such damages might be foreseeable. Telonics has no responsibility or liability for the claims of any third party. The maximum aggregate to the customer, of Telonics and its suppliers, shall not exceed the amount paid by the customer for the product.