Traffic Analysis of Small Telephone Switchboards

The emphasis in this work has been on maximal utilization under critical conditions, of the operator, lines, and subscribers, in the belief that in combat communications they are extremely important, and limiting factors should be known and understood so that corrective measures can be taken. This is shown by the difference in service between six or more subscribers, and between short and long conversations. Some of the results obtained are as follows. There are load conditions where the addition of a second operator does not improve service, in fact, it can be detrimental. Under some conditions the number of lines is the limiting factor, and with others the operator is the limiting factor. There are heavily loaded conditions where service is not much better with a fast board than with a slow board. A board which is 15 per cent faster may give an improvement of less than 1 per cent under some conditions. There are conditions that require subscribers to spend far more time in waiting and trying than in talking. Operations that take up the operator's time are multiplied to the subscribers, and result in much poorer service than is apparent just from the increase in operator occupancy. Adding a second line to a busy subscriber generally improves service to all subscribers. Dividing a given calling rate between more subscribers (or trunks) always improves service. Increasing the calling rate always makes for poorer service. Reducing message length always improves service. Long conversations are the greatest obstacle to good service. Conference calls can ruin service if prior conversations are allowed to continue without interruption.