covert%covert.DEC@decwrl.dec.com (John R. Covert) (10/05/88)
>While in Frankfurt last week I noted that phone numbers varied in >length from 4 to 10 digits, maybe more. The longer ones seemed >to be DID into PBXs. >How does the CO know when it has all the digits? Does it time >out, or do prefixes carry implicit lengths? Neither. The exchange begins processing the call after some short number of digits (as few as one or as many as four, depending on the exchange type and local dialing plan) and continues to send digits to the distant exchange until you stop dialing, the call is answered, or some significantly large maximum is reached. This allows the operator at at PBX to be, for example, 9591-0, and for there to be four digit extensions such as 9591-2323. Europeans think we are weird for insisting on a fixed length numbering plan. /john
dave@rutgers.edu (Dave Levenson) (10/10/88)
In article <telecom-v08i0152m04@vector.UUCP>, covert%covert.DEC@decwrl.dec.com (John R. Covert) writes: ... > Europeans think we are weird for insisting on a fixed length numbering plan. While variable-length numbering plans are convenient for number assignments, they are very expensive for the PTT or telephone company. When you are dialing a variable-length number, your local central office must send it to the distant office one digit at a time. This means that you occupy an inter-office digit-sender for as long as it takes you to finish dialing. In the Bell System, the fixed-length number is registered in the originating central office, buffered, and then sent as a complete address to the far end. This reduces occupancy of the interoffice sender equipment, requiring far less such equipment per central office. -- Dave Levenson Westmark, Inc. The Man in the Mooney Warren, NJ USA {rutgers | att}!westmark!dave