EP0254386A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Digital transmission system
Assignee: GPT Ltd
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Filing: 1987-04-13
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Granted: —
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Expires: 2007-04-13
Abstract
Abstract The invention concerns a terminal for a telephone system and for receiving digital data in the form of a time multiplexed (TDM) data stream incorporating frames appearing at a predetermined frame period and each frame incorporating a frame word. The terminal comprises frame word detecting means (52) for detecting frame words; alignment detecting means (53, 55, 56) for determining whether a received TDM data stream is in alignment or not; search means (53, 55, 56, 57, 59, 60) for initiating a bit-by-bit search of the incoming data stream for the sequence of bits forming the frame word when an "out-of-alignment" condition has been detected by the said alignment detecting means; and delay means (58) for delaying the start of the bit-by-bit search after an "out-of-alignment" condition has been detected.
Inventors
- 👤 Anthony Robin Thomas
- 👤 Stephen Patrick Ferguson
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 05:11
CPC Classifications
H; H04; H04J; H04J3/00; H04J3/02; H04J3/06; H04J3/0602; H04J3/0605; H04J3/0608
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
121 words
A terminal for receiving digital data in the form of a time multiplexed (TDM) data stream incorporating frames appearing at a predetermined frame period and each frame incorporating a frame word, the terminal comprising: frame word detecting means (52) for detecting frame words; alignment detecting means (53, 55, 56) for determining whether a received TDM data stream is in alignment or not; search means (53, 55, 56, 57, 59, 60) for initiating a bit-by-bit search of the incoming data stream for the sequence of bits forming the frame word when an "out-of-alignment" condition has been detected by the said alignment detecting means; and delay means (58) for delaying the start of the bit-by-bit search after an "out-of-alignment" condition has been detected.
Claim 2
Dependent Claim
121 words
A terminal for receiving digital data in the form of a time multiplexed (TDM) data stream incorporating frames appearing at a predetermined frame period and each frame incorporating a frame word, the terminal comprising: frame word detecting means (52) for detecting frame words; alignment detecting means (53, 55, 56) for determining whether a received TDM data stream is in alignment or not; search means (53, 55, 56, 57, 59, 60) for initiating a bit-by-bit search of the incoming data stream for the sequence of bits forming the frame word when an "out-of-alignment" condition has been detected by the said alignment detecting means; and delay means (58) for delaying the start of the bit-by-bit search after an "out-of-alignment" condition has been detected.
Claim 3
Dependent Claim
78 words
A terminal as claimed in Claim 1, and charactereised in that said frame word detecting means comprises: counting means (53) operative to reach a predetermined state on detection of a correctly aligned frame word; a master alignment store (56) held in an "in alignment" state when said counting means (53) is in said predetermined state; and inhibit means (60) operative to inhibit said master alignment counting means whilst said master alignment store is in said "in alignment" state.
Claim 4
Dependent Claim
41 words
A terminal as claimed in Claim 2, and characterised in that said frame word detecting means comprise a serial register (50) for receiving said TDM data stream and having a length at least equal to the length of a frame word.
Claim 5
Dependent Claim
27 words
A terminal as claimed in Claim 3, and characterised in that it includes gating means (52) for connecting said serial register (50) to said counting means (53).
Claim 6
Dependent Claim
36 words
A terminal as claimed in Claim 4, and characterised in that it includes a frame interval counter (55) operative to clock said counting means (53) each time a frame word is expected in said serial register.
Claim 7
Dependent Claim
46 words
A terminal as claimed in Claim 4, and characterised in that it includes means for altering the state of said counting means should a frame word not be present in said serial register (50) at the expected time as determined by said frame interval counter (55).
Claim 8
Dependent Claim
35 words
A terminal as claimed in Claim 6, and characterised in that out-of-alignment is determined by the failure to detect a selected number of frame words at appropriate times determined by said frame interval counter (55).
Claim 9
Dependent Claim
44 words
8 . A terminal as claimed in Claim 7, and characterised in that the delay is generated by a delay circuit (58) which is connected to said frame interval counter (55) and is arranged to inhibit said counting means (53) for a predetermined period.
Claim 10
Dependent Claim
28 words
A terminal as claimed in Claim 8 and characterised in that said delay circuit (58) is operative to generate a delay of one frame period minus one bit.
References Cited (Backward Citations)
No citation records indexed.
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