Arrow/ Times: Feb-Apr 2006

Control and Programming Switches for IPTU Set-Top Boxes

The continuing development of set-top boxes to offer an ever increasing range of services is taken one step further with the roll-out of IPTV (Internet Protocol Television). Offering a digital television service delivered to subscribing consumers using the Internet Protocol over a broadband connection is an exciting arena for new media. IPTV may also provide Video on Demand and Internet services such as Web access and VOIP. IPTV is expected to grow rapidly in the coming years as broadband is now available to more than 100 million households worldwide. Many of the world's major telecommunications providers are exploring IPTV as a new revenue opportunity from their existing markets and as a response to the growth of more conventional Cable Television services.

While the key to IPT is the growth of broadband and emerging software it also places new demands on the set-top box maker. A more sophisticated user interface is required and frequently internal configuration to suit global markets. knitter-switch has been working closely with set-top box manufacturers to understand these emerging requirements and provide RoHS compliant, high quality, cost effective solutions for high volume production.

To give the end user simple and effective control of front panel menu selection and switching, single and multi-function TACT switches are now the most common solution. For single board end product designs right-angle switches are required such as the TS 6xx-RA. A 90° mounted, through-board tact switch with a "sharp" click for positive tactile feedback and O.25mm travel. This is an ultra-miniature design for high-density mounting. Various actuator lengths are available from 3.15mm to 13mm and operating forces may be specified between 1009 to 52Og. Typical life expectancy is up to 1OO0k operations. For lower profile designs the TS 637 -RA offers very similar performance to the TS6xx-RA with a maximum height of just 3.0mm but is only available with 1609 operating force.

For SMD manufacture the washable TMSE 10J-RA 90° mounted tact switch has very compact dimensions of 5mm sq with a height of 5.44mm. With a "sharp" tactile click and soft silicone actuator for good pre-travel and a long activating travel of 1 .27mm. The TSS 4-RA ultra-miniature SMD 90° mounted tact switch has dimensions 3.5mm x 7.2mm x 3.5mm and a 200g operating force. These switches may be supplied on tape and reel, have large solder pads for reliable connections and are suitable for 260° C soldering.

For set-top box designs with front panels the ultra-low profile SMD 90° mounted tact switch TSS 313-RA has a height above the PCB of just 2.0mm, has an operating force 250g and is available with location posts for added strength of mounting. For through-PCB mounting the TMP 1 tact switch has rubber contact for a 'softer' tactile feel (ideal for low noise environments) and has a wide range of snap-on buttons available. Suitable for 270°C soldering and washable the TMP1 has a life expectancy of up to 1000k operations. For menu control and selection the TSSJ 55 SMD multi-function tact switch has 5 functions and an ultra-low profile of just 1.55mm, operating forces are 180g (side) and 320g (centre), and it can withstand 260°C soldering. In addition to use as a joystick the TSSJ 55 can be used to replace 5 conventional switches

For internal set-up and configuration two types of DIP-switch are available. The DHS900 is a SMD design on a 1.27mm half pitch to save PCB space. It has a 2.0mm low profile and gold plated terminals and contacts. Versions are available with 2,4,6,8.10.12 poles. The SBS 1000 is also an SMD switch on a 2.54mm pitch with 112poles available. Both switches have gold plated contacts and terminals, may be supplied on tape and reel and are suitable for reflow soldering at 260°C. The SBS 1000 may also be supplied in tubes for automatic assembly.