ASCO Model 138 (Edco RJA-RJD Series) Surge Protective Device

The ASCO Model 138 incorporates female jacks in and out. The ANALOG Model 138 voltage clamp is set for C.O. Trunks and Analog Telephone Extensions (with ring in voltage), and the DIGITAL Model 138 voltage clamp is set for Digital Extensions (no ring in voltage).


  • <1 nanosecond response time
  • Solid-state resettable fuses – PTCs
  • Silicon breakover technology
  • Low capacitance
  • Line-to-line protection
  • Accommodates RJ-11 jack
  • Tip & ring to ground protection
  • CAN/CSA C22.2, No. 226-92 compliant
  • UL 497A listed
  • 4 pair protection
  • 5 year warranty


  • Protects line-to-line, as well as tip and ring to ground.
  • Responds quickly to transients.
  • Exhibits low capacitance to support high-speed data rates 

Technical Specifications