Abstract: It is important to report alarm signals rapidly and reliably to the master control units responsible for automatically responding to these alarm signals. Advantageously this is accomplished by transmitting the alarm signals through a switching network of a telecommunications switch, using auxiliary signaling bits provided with each time slot that is switched through the network. The alarm signals are encoded in groups of eight, using one bit of each of eight related time slots to provide an alarm signal within one frame of a digital transmission signal.

Abstract: In order to provide reliable backup memory for the operational memory (RAM) of a control unit, two segments of a memory with write protect facility are used. Only one of these segments contains the backup memory at any one time, but the other segment may be updated with a new release. Write protect is removed from one of these segments only when an update is taking place. The software for controlling initialization of the operational memory from the backup memory is stored in the backup memory. Extensive checks are performed before accepting an update of the backup memory or an initialization of the operational memory.

Abstract: A method for changing the call handling capacity of a telecommunications switch requires authorization from an external source, such as a telecommunications equipment manufacturing company (TEMC). Each switch purchased from the particular switch manufacturer includes a customized upgrade security protocol which limits access to data bus blocks associated with integrated digital carrier units of the switch. To alter the upgrade security program, an authorization code must be retrieved from the TEMC. The authorization code is then entered into the switch, and used to automatically alter the upgrade security protocol so that previously blocked data buses may be activated.

Abstract: An Electrically Erasable Programmable Read Only Memory (EEPROM) provides backup and initialization data for random access memory (RAM) in a control unit. In order to update the EEPROM with new releases of a program and data, the EEPROM is divided into two segments, each with a separately controllable write enable voltage. Advantageously, this allows a new release to be written into one segment of a single EEPROM without erasing the other segment until the newly written segment has been verified. The software for controlling an update of the EEPROM is stored in RAM and the software for controlling an initialization of the RAM from the EEPROM is stored in the EEPROM. Extensive checks are performed before accepting an update of the EEPROM or an initialization of the RAM.