A telecommunications cable having a cable core in which each conductor is surrounded by an individual dual layer insulation of an inner layer of flame retardant polyolefin and an outer layer of fluorinated ethylene propylene. The cable is for plenum chamber usage in which smoke is to be minimized. Although the flame retardant polyolefin is a known smoke generating substance which does not satisfy plenum test smoke requirements, its use in this structure is entirely suitable for plenum chamber us...

In a telecommunications system in which narrowband or guiding services already exist, different service rates, either fixed or variable may be required. A further service switch is connected in parallel with the existing narrowband or guiding switch, the further service switch being similarly controlled in response to the guiding signalling.

A telecommunications connector with break/test facility includes a housing (10) which receives a plurality of pairs of contacts (42,44). The housing has a series of first chambers (40) and a series of adjacent second chambers (56). The first contact of each pair has and insulation displacement portion (102,104) received in the first chamber and a spring tail (114) which is received an anchored in the second chamber. The second contact has a conductor termination portion (80) which may be an insu...

In a telecommunications switching network which has a plurality of sub-networks, each sub-network having a plurality of User Network Ports, the Destination and Source addresses in a cell-header carrier by a cell switched by the network are each divided into a Port Address part and a Sub-Network Address part, the Source Sub-Network part being implicit while the cell remains in the Source Sub-Network and similarly the Destination Sub-Network part is implicit when the cell arrives in the Destinatio...

Error-free or rapid protection switching between two basestations, one main and one standby, or two transmitters (1,2) etc. of one basestation (8) is achieved using a downstream marshalling scheme involving the transmission of a sequence from the standby basestation to an outstation (9,10,11) at levels below the noise sensitivity of a receiver (7) at the outstation and alignment of the phases of the transmitted sequence and a reference main basestation sequence by, for example, a correlation pro...

A switching circuit includes a magnetically latching relay and associated contacts connected between a subscriber loop and associated subscriber equipment. In one state of latched operation the subscriber equipment is connected to the loop via the contacts and in the other state of latched operation the subscriber equipment is disconnected from the loop. To operate the relay a voltage is applied to the loop, the voltage being of sufficient value to charge a capacitor in the switching circuit to ...

Cordage suitable for use, for example, in spring telephone cords which connect a telephone handset to a telephone base and a line cord which connects the telephone base to a wall terminal includes a plurality of tinsel conductors individually insulated with a polyether polyester thermoplastic copolymer obtained by reacting 1, 4 butane diol terephthalate with terephthalate esters of polytetramethylene glycol and stabilized with a long chain hindered phenolic antioxidant, tubed over each of the co...

A connector block for telecommunication lines comprises a unitary structure including a protector field section, a cross-connect field section and a test field section. The cross-connect field extends down one side of the protector field facing in a direction to that which the protector field faces. The test field is positioned on the corner of the junction between the protector field and the cross-connect field, being inclined to face in a direction intermediate that of the protector field and ...

A protector field, as used in connecting units for telecommunications lines, comprises a metal housing having metal portions, the portions having formations at predetermined spaced apart positions to define protector positions. Terminals extend through an electrically insulating back member for connection to protectors, and for connection of conductors. The metal casing and partitions provide effective grounding means for the protectors. Formations on the portions cooperate with detents on the p...

A d.c. signal detector circuit for a telephone exchange which comprises a level detector which is so connected that it can sense current flowing in a telephone line. The level detector is arranged to switch states when a loop is established in a telephone circuit. Two level detectors can be employed to sense the establishment of a loop, a coin pulse, or an earth loop.