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It is shown that the CCSNo7 link availability depends on both the signalling load and signalling unit length if the signal unit error rate monitor (SUERM) algorithm is built according to current ITU-T recommendations. A rearrangement of the SUERM algorithm is suggested so that the link availability has the largest and most constant possible value for the prescribed BER.

A generalised model of the signal unit error rate monitor in CCSNo7 is described. It is shown that a desired link availability may be obtained by adjusting two parameters in the generalised model. The desired link availability may be, according to ITU-T recommendation Q.703, independent of load or equalised, and high and dependent on the signalling load and SU length.

A call collision reducing method for telephone networks using CCS no. 7 is suggested. The proposed method slightly increases the probability of blocking or waiting, but greatly reduces the probability of double seizure. Calculation of the collision and blocking probabilities for the new method is illustrated with an example.

An exact calculation of the minimum required power of a ringing signal generator in a telephone exchange is presented. The problem of power calculation is treated as a traffic problem. As can be seen, the required ringing power is a function of the traffic parameters of subscribers, the electrical characteristics of the telephone lines and sets, and the allowed overload time.

Two methods of mean CCSNo7 link alignment time calculation are suggested. One of these methods is also applicable for mean CCSNo7 link changeover time calculation. The results obtained are compared to results of known methods and simulation results.