These units are designed to be mounted (glue or bolt-on) the carapace of turtles.


Model Weight Standard Life Lifespan range Dimensions: L x Diameter (mm)
SI-2F 12g 12 months 6-18 months 33 x 11
SI-2F 14g 18 months 12-24 months 40 x 11
SI-2F 16g 24 months 12-30 months 50 x 11

Frequency Range: 138 – 235 MHz.

Transmitter: Crystal controlled two-stage design pulsed by a CMOS multivibrator.

Pulse Width (standard): 24 milliseconds.

Pulse Rate (standard): 35 pulses per minute (ppm). Available from 20-120ppm.

Power Output: Set to use available battery power over the required transmitter life.

Activation: Removing an external magnet starts the transmitter. Replacing the magnet stops the transmitter.

Housing: The battery and transmitter are hermetically sealed in a brass case.

Attachment: Brass tabs are attached at the mid-point or at the ends for screw attachment to a turtle carapace. The transmitter is usually mounted above a back leg.

Antenna: Stranded stainless steel cable covered with a black nylon coating. Additional layers of shrinkable tubing and/or a spring reinforce the antenna at its base.


Temperature (suffix “T”): An increase or decrease in temperature results in a corresponding increase or decrease in pulse rate. At the standard settings, the pulse rate changes from ~15 ppm at 0°C to ~40 ppm at 40°C. Each transmitter is supplied with a plotted calibration curve. This option adds ~0.05g to the finished weight of the transmitter.