The TCH Technology TCH Atlas-0621 locomotive decoder is suitable for Atlas 8-40BW and similar locomotives.
The characteristices of the decoder are:

• Full Back EMF control. Can be turned on and off with function controls
• Selectable for operation with 14/27,28/56 or 126/256 speed steps.
• Operation on conventional DC layouts is possible or can be disabled.
• Two (2) on/off function outputs with a current rating of 250mA each
• Speacial lighting effects including directional, independent, dimming, Mars light, Gyro light, single Strobe, and double Strobe.
• Support for Advanced Consist Control and Extended Addressing
• Support for programming on the mainline (ops mode)
• Provides 0.5 Amps continuouse motor current.
• Size L 1.45" x W 0.56" x H 0.12"

Full back EMF feedback control which can be set on or off with a CV. Two non-feedback motor modes

• Low frequency pulse width modulation (66 Hz non-adjustable)
• High frequency pulse width modulation (DC equivalent) at 20625Hz

Two feedback modes

• Low frequency pulse width modulation (66Hz non adjustable)
• high frequency pulse width modulation (20625Hz) with special low speed control

The proportional gain (Kp), integral gain (Ki),and the filter factor (Kf) are all adjustable with CVs so the feedback can be tuned to the motor. When used in the high frequency mode it is ideal for coreless motors but is equally suited for standard can motors wthich makes the usual buzz non existent. Using high frequency pulse width modulation lets both decoder and motor run cooler.