Etiquette - good telephone manners

Nineteenth-century British society is governed by a set of rules with a rigid format.  These rules determine (among other things) who may call on whom, and when; how visiting cards are to be used; how to interact with a family that has suffered a bereavement; how to give and receive invitations; and hundreds of other situations.

In the Fin de Siecle period, these rules are gradually relaxed, an atmosphere of informality begins to appear where people do not insist so much on social norms being enforced.

It is in this same period that the telephone makes its appearance in society.  Coincidentally, it is used in those circles where social manners were/are considered important.  (Not that the 'lower classes' didn't have their own social codes; they did, but their codes were untouched by the initial telephone's appearance.  Other technologies shaped their daily lives.)

My question - did the presence of the telephone in these people's houses play any fundamental, primary role in relaxing (or, subverting?) existing rules of etiquette?  Or did other factors come into play (e.g. the various changes in society that can be lumped together under the heading of Modernity)?  In other words, is the telephone the cause or the symptom of the erosion in social manners during this era?

In a domestic situation, the telephone starts off as a tool for 'business' (the business of running a household): ringing to place grocery orders, etc.  Prior to this, of course, it allowed the gentleman of the house to keep in touch with his place of business (his home is an 'extended office').  The telephone then ends up as a tool for conducting social relationships (giving invitations, asking after friends, etc.)

Then, as now, people express concerns about bad manners in phone use or the phone's intrusiveness in the domestic sphere.  See:

* Gary Marx.  "New telecommunications require new manners."   Telecoms Policy 1994 18(7); 538-551.

* Minna T. Antrim, “Outrages of the telephone,” Lippincotts’ Monthly Magazine Vol 84 (July 1909), 125-26.

* Maude A. White, “‘Those Telephonics.’  Have you one in your home?”  Delineator, Vol 96 (May 1920).

Sometimes, the new technology appears and embeds itself in social practice so quickly that it takes a while for the rules of good behaviour to catch up with reality and set out some ground rules for basic use.  A similar phenomenon is observed nowadays with mobile phones, e-mails, etc. (when should mobiles be turned off, do we treat e-mails like paper memos, etc.)