Abstract: An auxiliary connector circuit is used within an electronic system (10) which comprises a plurality of removable circuit cards (14, 16, 18, 20, 22, 24, 26) which are mounted within a cabinet (12). Before the circuit card (16) is removed from the cabinet (12), a power cable (44) is connected by means of engaging a plug (46) to a socket (34). When this occurs a DATA OUT ENABLE signal at a line (65) drives three-state devices (86, 88, 90, 92, 94, 96, 98 and 100) to a high impedance state to isolate a memory array (78) from a data bus (102). This high impedance prevents any transients from being transmitted through the data bus (102) when the card (16) is removed from the cabinet (12). After the card (16) is removed from the cabinet (12), the power cable (44) can be disconnected from the card (16) or the card (16) can be tested to evaluate the components mounted on the card (16).

Abstract: The present invention relates to improvements in communication procedures, especially in networks which include at least one device which is capable of being manually switched to an off-line condition. In accordance with the invention, when a switch on such a device is thrown to the position which would place the device in an off-line condition, the device formulates and transmits a message to indicate that it is going to a temporary off-line condition. This message can be used at other devices which are connected in the communication network. Such a message can be employed at a network focal point for maintaining such a device in a polling loop regardless of the fact that the device may, for some period of time, fail to respond to any polls. Such a message can also be employed in any device which was in active communication with the device at the time it was placed in the temporary off-line condition to queue a restart request.

Abstract: In a data message communication system, certain messages require a return acknowledgement signal. The present invention contemplates a method and means which are activated whenever an outbound message is received. Each portable unit which receives a message then monitors the outbound communication channel to determine if the inhibit signal is currently active. If the inhibit is not currently active, the particular unit will transmit its acknowledgement message immediately. If the inhibit signal is active, each portable unit will maintain a count of the number of outbound messages, addressed to other units requiring an acknowledgement, since that particular portable received its message. At the termination of the inhibit signal, each portable unit will pause for a period equivalent to the product of the acknowledgement message time slot multiplied by count of messages accumulated since the receipt of the particular portable units message.

Abstract: A hand-held remote control transmitter for controlling a plurality of functions in a number of different devices includes a matrix keyboard comprising keys operating two independent switches with a single depression, with the first switches selecting a memory page in an IC and the second switches selecting a function code on the page by the X-Y key closure. A multi-position device switch accesses the memory page associated with the selected device. The first switches of each of a group of redefinable keys that perform the same functions in each of the different devices are connected to the multi-position device switch. The independent switches are formed by overlying two conventional membrane switches with the lower one providing tactile sensation.

Abstract: In a ring network (1) messages sent from any one of a group of stations (3) to all the remainder include an acknowledgement field (ACK) holding a count preset to equal the number of expected destination stations. Each destination station that successfully receives the message acknowledges by decreasing the count by 1; acknowledgement is withheld if an error is detected in the message or the station cannot accept it. Acknowledgement is performed by a circuit (17) in a loop-through path (15) in an interface unit (4) connecting the station to the network (1). The originating station checks in a circuit (28) if the final value of the count on its return is zero. If so, the originating station is assured that each expected destination has made a positive acknowledgement of successful receipt.

Abstract: A decentralized local communication network comprising a plurality of stations. A right to transmit data on a traffic channel, to which each station is connected, is allocated by means of a token. At least one priority level indicating a frequency of allocation of the token assigned to each station, the stations having the same priority level form part of a same group and are assigned to a logic loop for the circulation of the token. The network comprises at least two logic loops. With each priority level there is associated a predetermined time interval which corresponds to a period of time expiring between two successive allocations of the token to a station of the group having said associated priority level. Upon expiration of one of said time intervals, the token passes to the logic loop which is associated to the priority level for which said time interval was expirated and starts to circulate in that logic loop.