changePropagationDelay(delay) {
        if (this.propagationDelayFixed) return;
        if (delay === undefined) return;
        if (delay === '') return;
        var tmpDelay = parseInt(delay, 10);
        if (tmpDelay < 0) return;
        this.propagationDelay = tmpDelay;
    }
Method to change object delay
OVERRIDE if necessary
@param {number} delay - new delay