INTERNATIONAL TELECOMMUNICATION UNION ITU-T RECOMMENDATION SUMMARY Rec. No. : K.28 Title : Characteristics of semi-conductor arrester assemblies for the protection of telecommunications installations Study Group : V - Protection against Electromagnetic Effects Version : New Date of adoption : 1991 Notes : Careful survey of the electrical environment that telephone equipment must safely survive, has led to the conclusion that semi-conductor devices that are robust enough to act as primary protectors are now possible. Semi-conductor devices provide for tightly toleranced and stable over-voltage control, which does not change with age or activity within their design capability. Furthermore, they introduce negligible circuit noise on the circuits they are protecting. Widespread trials of these semi-conductor overvoltage protectors for primary protection are taking place and Recommendation K.28 provides detailed guidance on the particular qualities which should be sought when manufacturing or purchasing such devices. The trials and initial applications are ongoing and some details of the technology may change in the light of the results. Nevertheless, to bring the trials and initial applications to the notice of a wider audience and to acquaint potential users with both the advantages and disadvantages of these devices, CCITT considers the subject to be important and stable enough to publish a Recommendation on the new technology. The purpose of Recommendation K.28 is to provide technical guidelines for purchasers and manufacturers of semi-conductor arrester assemblies (SAA) to ensure their satisfactory operation in the applications for which they are intended. It is intended to be used for the harmonization of specifications issued by manufacturers of semi-conductor arrester assemblies (SAA) and network operators. Only minimum requirements are specified for essential characteristics. As some users may be exposed to different environments or have different operating conditions, service objectives or economic constraints, the requirements of Recommendation K.28 may be modified or further requirements added to suit local conditions. It is for Administrations to classify the environment for a particular device, taking into account business policy, and economic and technical considerations. To order the complete text of this Recommendation, please use the Order Form for ITU-T Recommendations. An electronic version of this form is available on ITUDOC (Winword 2.0: UPI=ITU-5265; ASCII: UPI=ITU-2488).