since the If full time call management information is critical, then interface data is processed off-line. Distribution of product to individual failure detection processes should be provided between the switch customer departments can occur directly from the service bureau. and call management system. Since producing call management The disadvantages of the service bureau are that flexibility and information may be a minor objective for the switch, failure detec- control may be lost. The customer is now dependent upon the tion becomes the responsibility of the call management system. An service bureau's schedules, product revisions, and cost structure alarm, either audible or visual can be generated if call information, changes. or keep alive data, is not received as expected within a specified time period. If the detection is based on receiving call records, then 36.4.2 User owned systems the process should adjust to lack of records that may naturally occur during some times in the day. The alternative to the service bureau is for the user to own, or lease, The data buffer capacity in the switch and call management the call accounting system. The hardware and software may be system should be considered, for this becomes an important factor acquired from the same vendor; however, most PC-based software during out of service periods. Standard buffer and optional expan- systems are sold independently. The user may also choose to per- sion increments should be considered against the requirements. If form the software development. buffer capacity is 10,000 records, the switch produces one call detail The advantages of the user owned system are that reporting record per call, and the call rate is one call per second, then the alternatives are just as available as provided by the service bureau. buffer can hold call records for 2 hours, 46 minutes and 40 seconds. The software vendor may offer alternative packages, or the package If the requirement is to support an out of service period of 4 hours, may allow report sel