ADVANCED REMOTE CONTROLLERS
Advances in technology and consumer demand have led to many ‘special’ types of remote control, primarily designed to make operation simpler for the user; to replace lost or faulty units; and to facilitate house-wide operation. They are described below.
Learning and ‘Universal’ types
Learning remote controls have both an IR receiver and an IR emit- ter at the front end. To ‘teach’ them the commands for any piece of equipment, the original handset is placed head to head with the new one, and the latter set to receive mode. Now the commands are passed into the new handset and stored in memory for reproduction in send mode. At the press of each key the code of the original is mimicked, and this type of remote control can learn and reproduce the codes for several different pieces of equipment: TV, VCR, satellite, audio etc.
An alternative technology, especially useful where the original handset has been lost, is the Universal remote control. Stored in memory inside it are thousands of control-code groups for a huge range of TV/video/audio home-electronics products. For any given piece of equipment the required code can be called up (found by trial and error if necessary) and assigned for use. Again several different equipments can be controlled from the one handset using a selection key.
Extenders
Infra-red light beams cannot travel through walls or floors and when (as is often the case) there is an r.f. distribution system in the dwell- ing, the need arises to control it from one or more of the remote TV sets. An extender system has two components, a receiver and a relay, both mains powered. The receiver module is placed near the remote TV to pick up infra-red commands there and convert them to a radio transmission, typically at a low-UHF frequency of 418 MHz. That is picked up by the relay module, placed in sight of the equipment in the living room, to which it radiates reconstituted IR commands, mimicking those of the original handset: TV, video, audio and satel- lite equipment can thus be controlled. A variant of the system uses a clip-on (battery-powered) module at the front of the remote control handset to extend its range house-wide.
LCD-programming handsets
For use with VCRs, some handsets have an LCD display built in: its drive electronics are incorporated in an encoder IC of the type already described, along with a small data register or memory. For timer programming, all the required data of date, start/stop times, TV chan- nel and recording speed are composed by the user in the LED display on the handset and written into the data register. When it is complete a ‘transmit’ prompt appears in the display and a stroke on the ‘send’ key conveys all the data in the register via the IR control link to a similar register in the VCR. Here it is decoded and briefly displayed – on the front panel readout – for confirmation, then stored as timer information to be actioned when stored time and real-time data matches.
A simpler programming system, also using an LCD handset, is the VideoPlus concept by Gemstar. Here each TV programme has its own numerical code consisting of 3–7 digits, printed in newspapers and programme guides. Keying this number into the handset while in VideoPlus mode permits its assembly into a data register, and subsequent transmission to the VCR where (in conjunction with the real-time clock data) it is decoded into start/stop times and TV channel data for action when the programme is transmitted.
Another type of LCD handset is used in conjunction with sophisticated digital satellite-radio systems of the sort described on page 93. Alongside the normal IR transmission LED is a receiving IR photodiode, responsive to a data-transmitting LED on the sat- radio set’s front panel. Along with the audio data, information on the channel, track title, artist, composer, CD reference number etc. is broadcast, and this is transcoded to an IR datastream for passage back to the user’s handset and display in its LCD panel.
PDC programming
Timer-event programming by manual or VideoPlus means cannot properly capture a TV transmission which is rescheduled in time, or is delayed by (e.g.) a previous programme overrunning its time, as may happen to ‘live’ news or sport coverage. Neither of these systems have any link to the programme’s identity beyond its published date, time and transmission channel.
To overcome this problem, all broadcasters are party to the PDC (Programme Delivery Control) system, in which the recording action is triggered by data sent with the programme transmission itself: this can cater not only for late running, but for complete rescheduling of the wanted programme, on the expected channel, or on any other which the tuner can receive and is logged in its tuning memory.
PDC data is incorporated in the teletext signal, where it occupies packet 8/30, not displayed on the teletext screen. The transmission and decoding of teletext data was covered in Chapter 8, and applies equally to the PDC signal, though here the decoding circuit is much simpler, as the IC diagram of Fig. 22.3 shows. The broadcast video signal enters on pins 1 and 2 where text and sync pulses are gated out and passed to a data-acquisition stage whose address cor- responds only to text packet 8/30, transmitted once per second on TV line 16. The data it contains is thus extracted and held within the IC’s register, looking for a coincidence between the user’s timing instructions (entering from the system-control section on the I2C lines SDA and SCL, details later) and the stored PDC data. When they correspond instructions for channel selection and record mode are output on the same data bus and so the recording commences, terminated later by off-air instruction at the end of the broadcast programme. Apart from the video input and the I2C bus line links on pins 8 and 9 the other connections to the chip are mainly concerned with ‘housekeeping’ functions: the RC network at pin 17 is a loop filter for the PLL; pin 12 provides a flag to indicate recep- tion of PDC data; pins 14 and 11 provide test facilities; and the clamp reservoir capacitor at pin 5 stores the operating level for the adaptive sync separator.
User instructions come via the remote control keypad as time/date/ channel or VideoPlus data; it is converted within the VCR to a ‘packet’ form suitable for PDC programming. In many late-model VCRs the system control IC incorporates the PDC dataline decoder.