High impedance protection schemes are widely used for the protection of BUS bars, generators, motors & power transformers. BUS bar protection schemes utilizing electromechanical high impedance differential relays are often used due to their simplicity, reliability & comparatively low cost. While numeric high impedance differential relays are now available the application of electro mechanical schemes is likely to continue at least in the role of the Y protection scheme where duplicate protection is employed. The 1M123 system is an integrated protection scheme which overcomes the issue of space constraints on the protection panel & the problem of where & how to mount the Metrosil elements. The provision of at least one high speed multi trip relay is normally required and often a trip supply supervision element. All of these functions have been incorporated into a single tier, 4U high, 19 inch sub rack frame.