Signal Code.  The code by which stations are designated on non-selective party lines usually consists in combinations of long and short rings similar to the dots and dashes in the Morse code.  Thus, one short ring may indicate Station No. 1; two short rings Station No. 2; and so on up to, say, five short rings, indicating Station No. 5.  It is not good practice to employ more than five successive short rings because of the confusion which often arises in people’s minds as to the number of rings that they hear.  When, therefore, the number of stations to be rung by code exceeds five, it is better to employ combinations of long and short rings, and a good way is to adopt a partial decimal system, omitting the numbers higher than five in each ten, and employing long rings to indicate the tens digits and short rings to indicate the units digit, Table X.

TABLE X

Signal Code
+--------------+---------------+--------------+-------------

--+
|STATION NUMBER|RING           |STATION NUMBER|RING           |
|1             |1 short        |12            |1 long, 2 short|
|2             |2 short        |13            |1 long, 3 short|
|3             |3 short        |14            |1 long, 4 short|
|4             |4 short        |15            |1 long, 5 short|
|5             |5 short        |21            |2 long, 1 short|
|11            |1 long, 1 short|22            |2 long, 2 short|
+--------------+---------------+--------------+-------------

--+

Other arrangements are often employed and by almost any of them a great variety of readily distinguishable signals may be secured.  The patrons of such lines learn to distinguish, with comparatively few errors, between the calls intended for them and those intended for others, but frequently they do not observe the distinction, as has already been pointed out.

Limitations.  With good telephones the limit as to the number of stations that it is possible to operate upon a single line is usually due more to limitations in ringing than in talking.  As the number of stations is increased indefinitely a condition will be reached at which the generators will not be able to generate sufficient current to ring all of the bells, and this condition is likely to occur before the talking efficiency is seriously impaired by the number of bridges across the line.

Neither of these considerations, however, should determine the maximum number of stations to be placed on a line.  The proper limit as to the number of stations is not the number that can be rung by a single generator, or the number with which it is possible to transmit speech properly, but rather the number of stations that may be employed without causing undue interference between the various parties who may desire to use the line.  Overloaded party lines cause much annoyance, not only for the reason that the subscribers are often not able to use the line when they want it, but also, in non-selective lines, because of the incessant ringing of the bells, and the liability of confusion in the interpretation of the signaling code, which of course becomes more complex as the number of stations increases.