The first stage is comprised of a differential gas discharge tube. Stage two is a PTC resettable fuse and the third stage is a low capacitance diode array. The second stage series resistance limits the power dissipation of the third stages faster diode clamp array. This allows time for the slower but higher power gas tubes to turn on. The diode array clamps the leading edge of fast transients to safe levels until the high power gas tubes turn on. This eliminates the damaging leading edge spike that single stage gas tube protectors let leak through. The use of resettable PTC fuses minimizes downtime. In the case of an overload, the PTC fuse switches to a high impedance state. The PTC fuse will return to a low impedance state after cooling down. The low capacitance of the diode array assures that the high speed signals will not be degraded by the suppressor. The design utilizes a Thyristor diode which switches to a low impedance state once triggered. This offers superior power handling capability compared to TVS or Zener diode based designs. The limits are +/- 58 volts on the four cable pairs. The 3-stage design can handle higher-level transients than a protector that uses only diodes. For more complete surge protection of data lines, the use of two units is recommended, one at each end of the line.
