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1. Introduction

The Aleph Hadron Calorimeter [2][1] ,Hcal in short, is an iron-plastic streamer tube sampling calorimeter with a readout of 4608 analog signals coming from "towers" and 137 976 digital (i.e. yes-no) signals coming from readout strips. The active part is a sandwich of streamer tube planes inside the Aleph magnet iron return yoke. This is a massive iron cylindrical box with 2 meter thick walls, enclosing the inner part of the detector. The Muon detector, Mdet in short,consists of 88 muon chambers in two layers which completely surround the Aleph detector. Here the active elements are planes of streamer tubes read by a set of orthogonal strips, to measure the point where the particle has crossed the chamber. The total number of strips is 89 144. Each fired strip will give a digital (yes/no) signal. In the past,the monitoring of similar apparatus was done by using an event display showing the two signals (digital+analog) in such a way that their correlation was evident. In addition histograms were used to check for dead channels,pedestals,etc. The same tools ,when used to control our detector,although still useful, have some limitations, due to the complexity of the detector:

• An event display looks almost empty, so it is very difficult to pinpoint problems looking at single events.
• The number of histograms and scatter plots that one has to look to get some idea of what is going on is too big. Also,it is difficult to correlate the information in different histograms.
• The apparatus will run for years, so we have all the interest to make the maintenance operations easy and quick.