Plug-in bypass module for a cable TV network distribution tap

Abstract

A plug-in bypass module 40 configured to be connected between connector terminals 20, 20’ of a back box 10 (Figure 1), the module comprising a housing 46 (Figure 3) within which is located a power pass bar 42 and an actuation element 44, wherein the power pass bar comprises a central portion 50 (Figure 5) disposed within the housing and two end portions 52 (Figure 5) disposed external to the housing, the power pass bar moveable in response to the actuation element to create an air gap between each end portion and support blocks 22, 22’ (Figure 5) on which connector terminals in a back box are mounted. Each end portion may be angled relative to the central portion. The actuation element may be located centrally in the housing. Cams 26, 26’ (Figure 5) may deflect the end portions when the actuation element is activated.

Description

A Cisco / Scientific Atlanta back box 10 is shown in Figure 1 and comprises back box housing 12 with network input connection 14 and network output connection 16, connector terminals 20, 20’ each surrounded by a respective plastics connector support block 22, 22’, power pass bar 24 extending between connector terminals 20, 20’ and an actuator switch 26 for disconnecting power pass bar 24 from connector terminals 20, 20’ when a faceplate is mounted on back box 10. Channel 30 extends between connector support blocks 22, 22’ and has a central groove 32 to receive power pass bar 24 when it is deflected downwards by actuator switch 26 and disconnected. In distribution taps, the operational bandwidth above 1.2GHz is limited due to coupling between the connector blocks and the bypass bar. This is significant on a Cisco / Scientific Atlanta back box because when a faceplate is fitted and actuator switch 26 activated, power pass bar 24 slides downwards into groove 32 as shown in Figure 2 but remains in physical contact with connector support blocks 22, 22’ in region 34. This results in a high capacitive coupling between connector terminals 20, 20’ and the disconnected power pass bar 24 and limits the operational frequency of a Cisco / Scientific Atlanta back box to below 1.2GHz. To resolve this issue and as shown in Figures 3 and 4, the existing bar 24 and actuator 26 are replaced with a pre-assembled bypass module 40 incorporating a power pass bar 42 and actuator switch 44 to ensure lower capacitive coupling when a faceplate is fitted and so the ability to operate above 1,2GHz. Module 40 comprises a substantially rectangular insert 46, typically moulded from plastics material, and configured such that module 40 sits within channel 30 after power pass bar 24 and actuator 26 have been removed. Power pass bar 42 is generally located within insert 46 but as shown in Figures 3 and 4 protrudes from opposing ends of insert 46 so as to be able to contact terminals 20, 20’ when a faceplate is not mounted on back box 10. Power pass bar 42 is configured such that when a faceplate is fitted, power pass bar 42 does not physically contact terminals 20, 20’ nor support blocks 22, 22’ and instead is levered away from support blocks 22, 22’ so as to ensure an air gap between power pass bar 42 and support blocks 22, 22’ and terminals 20, 20’. This produces a lower capacitive coupling and ensures the operational frequency of a Cisco / Scientific Atlanta back box can be extended above 1.2GHz without physically removing the back box from the CATV network. Power pass bar 42 can be levered by using one or more fixed pivot points within insert 46 or by using cams as shown in Figure 5 where power pass bar 42 comprises a central section 50 and angled end sections 52, 52’. When button 26 is pushed downwards by faceplate actuator bar 53 as faceplate 54 is fitted to the back box (not shown), fixed cams 56, 56’ urge against end sections 52, 52’. Due to the resilience of the metal from which power bar 42 is formed, end sections 52, 52’ temporarily alter their angle of deflection and so move away from terminals 20, 20’ as shown by arrow 58 and so move away from connector support 22. Thus by using module 40 fitted between terminals 20, 20’ within a Cisco / Scientific Atlanta back box, an installer can upgrade the operational frequency of network infrastructure with significantly reduced downtime compared to full tap replacement. The replacement bypass module incorporating the MBB switch can be of modular or cassette form. Whilst the existing power pass bar 24 and actuator switch 26 in back box 10 can simply be removed by prising them out with a medium sized flat bladed screw driver and then replacing with module 40, this interrupts the signal and power passing through the switch to downstream network equipment until the module is fitted, which is not desirable. To replace the MBB switch of power pass bar 24 and actuator 26 in situ without interrupting the network power to downstream devices, a jumper tool 60 is provided as shown in Figures 6 and 7 to electrically connect terminal 20 to terminal 20’ prior to the removal of power pass bar 24 and switch 26 and so ensure signal and power continue to pass through back box 10 as module 40 is positioned within back box 10. Jumper tool 60 comprises a housing 62 comprising a U-shaped central body 64 with first and second end portions 66, 66’ formed at approximately 90 degrees to central body 64. The central body 64 thus extends laterally to end portions 66, 66’. Within casing 62 is an insulated length of conductive wire 70 which connects at each end via solder 71 to an electrically conductive biased clip 72, 72’ with a cut-away portion 74, 74’ in housing 62 enabling each clip 72, 72’ to contact its associated terminal 20, 20’, see Figure 7. Each end portion 66, 66’ contains an internal seat portion 76, 76’ to rest on terminal 20, 20’. When jumper tool 60 is pressed into position over terminals 20, 20’, it electrically and physically connects to connector terminals 20, 20’, see Figure 8, whilst not disturbing the positioning of bar 24 and the connection of bar 24 connection to terminals 20, 20’. Jumper tool 60 diverts current away from power pass bar 24 and the shape of jumper tool 60 enables easy access to power pass bar 24 and switch 26 for removal and replacement because the lateral displacement of body 64 ensures that an operator can remove power pass bar 24 and switch 26 directly from above without being impeded by central body 64, see Figure 9. The existing power pass bar 24 and switch 26 are then removed and replacement MBB switch module 40 inserted, see Figure 9. Jumper tool 60 is then removed, ready for the faceplate to be reconnected. In this way, use of module 40 ensures the operational frequency of a Cisco / Scientific Atlanta back box can be extended above 5 1 2GHz without physically removing the back box from the CATV network.

Claims

1. A plug-in bypass module configured to be connected between connector terminals of a Cisco / Scientific Atlanta back box, the module comprising a housing within which is located a power pass bar and an actuation element, wherein the power pass bar comprises a central portion disposed within the housing and two end portions disposed external to the housing, the power pass bar moveable in response to the actuation element to create an air gap between each end portion and support blocks on which connector terminals in a Cisco / Scientific Atlanta back box are mounted.

2. A plug-in bypass module according to Claim 1, wherein each end portion is angled relative to the central portion.

3. A plug-in bypass module according to Claim 1 or Claim 2, wherein the actuation element is located centrally in the housing so as to act on the power pass bar.

4. A plug-in bypass module according to any of the preceding claims, wherein cams are located within the housing to deflect the end portions when the actuation element is activated.

5. A plug-in bypass module according to any of claims 1 to 3, wherein one or more pivot surfaces are located within the housing to alter placement of the power bar when the actuation element is activated.

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