The JavaScript below contains the template that must be used when setting up the tracking script.
<script type="text/javascript">
    var _ctq = _ctq || [];
    _ctq.push(['setSiteId', Site ID]);
    _ctq.push(['requires', [Group 1, Group 2, ..]]);
    // Insert calls to replacement methods here
    _ctq.push(['trackPageView']);

    (function() {
        var wca = document.createElement('script'); wca.type = 'text/javascript'; wca.async = !0;
        wca.src = "//web-call-analytics.com/wca.js";
        var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(wca, s);
    })();
</script>

Calls to replacement methods (described in the Methods section) must be inserted into this tracking script to enable number switching.