RECS: Customer Feedback



	Customer Feedback

Last update: Thu Dec 16 14:48:30 MET 1999

#1 - 09.09.1999
Q:	5:P12 declares that peripheral rooms are not controlled by the system and will not be described anymore. This is fine, but makes the distinction "offices" vs. "other rooms" muddy: do other rooms include peripheral rooms? Strictly speaking, since peripheral rooms are rooms, the answer should be YES. However, common sense dictates that the expression "other rooms" really means "computer labs, hardware labs and meeting rooms". This will turn out to be relevant in subsequent requirements.
A:	Exchange "other rooms" by "computer labs, hardware labs and meeting rooms".

#2 - 09.09.1999
Q:	The expression "if nothing else is desired by the chosen light scene" in 9:U1 may give way to some ambiguity. Does U1 mean that in setting an ambient light level any input below 14 lux should be regarded as invalid? Or that any light setting below 14 lux should be ignored, and a minimum light level of 14 lux should be established instead? Also, U1 is formally inconsistent with 9:U5 (a person can turn the lights off while occupying a room!) and possibly others...
A:	Look at answer of Q36. Each room user may override the "safe illumination" requirement.

#3 - 09.09.1999
Q:	9:U2 declares that as long as a room is occupied, the chosen light scene has to be maintained. This too is inconsistent with any form of user override (e.g., 9:U5). I interpreted "maintained" as "the system should (with a given frequency) update the dim values of the luminaries in a room so that the desired ambient light level of the current scene of the room is achieved in that room, keeping into account any light that comes through its windows". This however makes 9:U10 redundant, so maybe a different interpretation was intended.
A:	The chosen light scene has to be maintained in occupied rooms (9:U2), if nothing else is requested by the user. 9:U10 is independent of the room occupancy.

#4 - 09.09.1999
Q:	In 9:U8, the user of a room is introduced. The dictionary defines an "user" (of a room) as a person occupying a room, so I assume that "informing the user" really means "displaying something on the room control panel's display". Analogously, I assumed that "inform the facility manager" means "display something on the FM control panel".
A:	Yes, these assumptions are true.

#5 - 09.09.1999
Q:	9:U10 states that the light groups in an office should be maintained depending on the current light scene. This is ok, but some more detail about the way the customer wants them to be "maintained" would be welcome (see Q3).
A:	See answer of Q3.

#6 - 09.09.1999
Q:	10:FM1 requires that daylight should be used whenever possible to achieve the desired light setting in a hallway section. This seems to me a very rare occurrence, since hallway sections don't have any window (per Figure 1)!
A:	The windows are above the drawing-plane of 4:F1, and the doors can be open, see answer of Q10.

#7 - 09.09.1999
Q:	It is not clear from 10:FM9 if the system computes energy consumption based on his wishes of if it has any means to measure actual energy consumption. In particular, the light groups status lines only report an "on/off" status, with no indication about the current dim value. If the system bases the calculation only on the dim values it has set, this requirement is inconsistent with any form of manual override (or at least inaccurate). Also, no indication is given about the grain of the reports: I assumed that energy consumption is computed, and the past consumption log updated, every T4 minutes, with T4 settable by the facility manager.
A:	Energy consumption needs only be calculated based on the available information. Malfunctions that are neither detectable nor manually entered, can not be taken into account. But all dim values - as set by the control system - should be considerd. Usage of a settable time interval T4 is useful.

#8 - 09.09.1999
Q:	10:FM11 refers to "malfunctions that the system cannot detect". Since a malfunction could occur to some malfunction-detection component, potentially any kind of malfunction could be undetectable at some point, so the above specification is not useful. I assumed that any malfunction can be entered (manually) by the facility manager.
A:	Yes, this assumption is true.

#9 - 09.09.1999
Q:	In 10:NF2, the failure of an outdoor light sensor causes the setting of the default light scene "for all rooms". I interpreted that as "for all rooms whose windows have the same exposure as the failed outdoor light sensor". BTW, this relation should be made more explicit in Part 2; missing that, the only relation between a room and a light sensor is based on them both belonging to the same section (and that would be wrong, since sections don't have a single exposure!).
A:	"For all rooms" means all rooms, for which the calculation of indoor illuminance depends on the corresponding outdoor light sensor. Relevant is only the exposure of the windows of the room and the exposure of the failed outdoor light sensor.

#10 - 09.09.1999
Q:	As in Q6, 10:NF3 seems to imply that hallway sections have windows, that is in contrast with 4:F1.
A:	Firstly, doors between rooms and hallways can be open, this should be detected and taken into account. Secondly, above all doors which connect rooms with hallways, there are indeed small windows, through which the light of the rooms can fall into the hallways.

#11 - 09.09.1999
Q:	10:NF5 is a requirement on the dimmer-actuator, not on the control system. If a light group is controllable neither automatically nor manually, there is no way for the control system to ensure that the lights are on... Note that the prescribed behaviour is already part of the definition of a dimmer-actuator in 8:P19.
A:	This observation is right.

#12 - 09.09.1999
Q:	In the dictionary, 12:"default light scene" is defined as a light scene for the case that a room is NOT occupied. This is in contrast with 9:U4, where it is stated that the default light scene should be used when the room IS reoccupied after more than T1 minutes since the last person left the room. I assumed that U4 was the right interpretation.
A:	Yes, this assumption is correct.

#13 - 09.09.1999
Q:	What is the meaning of "turning on" and "off" the lights in 10:FM6? "Turn off" is to set the dim value to 0? "Turn on" is to use the default light scene (or a chosen light scene)?
A:	"Turn off" is to switch off the light, where the dim value may remain unchanged. "Turn on" is to switch on the light with a dim value of 100%.

#14 - 09.09.1999
Q:	Who uses the status lines of the dimmable lights? Why they are used? [8:S2.10]
A:	The control system uses the status line to detect manual operations of the dimmable light (use of push buttons).

#15 - 09.09.1999
Q:	What is the meaning of resolution of a sensor? [7:T1]
A:	The resolution of a sensor is the closest possible difference of two measured values.

#16 - 09.09.1999
Q:	What is the meaning of "calculation of light"? Is this procedure is a math formula? [7:T1."outdoor light sensor"]
A:	"Calculation" means the computation of the light status ("on"/"off") and the dimmer settings. This might be done by a math formula that has to be developed.

#17 - 09.09.1999
Q:	Daylight will be used to achieve the illumination level desired by the control system. How? Through windows? Can the windows be closed? Are they often closed for some reason? [10:FM1]
A:	Yes, daylight comes in through the windows. You can assume that the transmission of light through a window does not depend on the fact if it is closed or open.

#18 - 09.09.1999
Q:	What shall happen when a ceiling light group stops working? [9-11:S3]
A:	If this malfunction is entered manually, the system should take this into account, when calculating illuminations or energy consumptions.

#19 - 09.09.1999
Q:	What are unreasonable inputs? [11:NF9]
A:	For each input there exists a set of possible inputs and a set of valid inputs. The valid inputs are a subset of the possible inputs. Unreasonable inputs are possible, but not valid inputs. The sets of valid inputs still have to be defined.

#20 - 09.09.1999
Q:	Which hazardous conditions could happen? [11:NF7]
A:	People could tumble and fall because of sudden darkness due to switching off lights. Further situations might be proposed by the system developer.

#21 - 09.09.1999
Q:	The type of an actuator describes it's function on the control system or is a more general category of an actuator? [7:T2]
A:	"Type" describes its function. It is used by the control system to control an environmental quantity.

#22 - 09.09.1999
Q:	What is it an actuator? Is it a device that controls another device? [7:P18]
A:	It is used by the control system to control an environmental quantity, here for example also via the device "dimmable light".

#23 - 09.09.1999
Q:	Why there is a motion detector above the doors of the hallways? Why not only door closed contacts? [6:P16.1]
A:	This is a property of the existing installation.

#24 - 09.09.1999
Q:	What is the meaning of "range" of a sensor or actuator? [7:T1,7:T2]
A:	The range of a sensor is the interval in which reliable, measured data can occur. The range of an actuator is its interval of settable outputs.

#25 - 09.09.1999
Q:	What is the use of the door closed contact sensor? What actions of the systems are based on its value? [7:T1]
A:	It can be used to obtain additional information concerning occupancy and transmission of light, e.g., the occupancy of a room with closed doors can not change, or the light can only fall through open doors.

#26 - 09.09.1999
Q:	What is the default illumination of the default light scene? [9:U4,13:"light scene"]
A:	It is defined by the facility manager as a part of the default light scene.

#27 - 09.09.1999
Q:	Who defines a light scene? [9:P24]
A:	All light scenes, besides the default light scene, are defined by the user. The default light scene is defined by the facility manager.

#28 - 09.09.1999
Q:	When some malfunction occurs and the default light scene is chosen, what happens when the system comes back to normal operation? Does it restart the chosen light scene that was in use before the malfunction or does it keep the default light scene? [9-10:S3.1-S3.2]
A:	It restarts the chosen light scene.

#29 - 09.09.1999
Q:	Do all rooms have always two ceiling light groups? Can a room have just one ceiling light group? Can it have three or more? [5:P8.2]
A:	See Q38.

#30 - 09.09.1999
Q:	Is there any standard that might be used to check if the system is easy or intuitive? Is there any similar system in operation? [10:NF8]
A:	This question can not be answered precisely.

#31 - 09.09.1999
Q:	Where can DIN standards be found? [11:NF6]
A:	Detailed standards would only be important for the real physical realisation of hardware. They are not of interest here.

#32 - 09.09.1999
Q:	Is there any possibility of extension of the system, of using it on other floors, places etc? [9:Part3]
A:	No. This needs not to be considered.

#33 - 09.09.1999
Q:	What's the meaning of stepwise degradation in 10:P30? How this can be accomplished?
A:	"Stepwise degradation" means that 1) in case of a local malfunction the remaining parts of the control system should still work and 2) different requirements have to be fulfilled for the damaged control system part. A list of possible malfunctions and restricted requirements should be proposed by the system developer for a later review by the customer.

#34 - 09.09.1999
Q:	10:FM10 says that malfunctions and unusual conditions should be reported on request. To whom will they be reported? What is the meaning of "on request"? Does it includes major failures? Isn't something like an audible alarm, missing?
A:	The facility manager will receive this information, but only on request. An audible alarm is not necessary. "On request" means that the facility manager has to ask the control system for a report. He can request and receive this report via his control panel.

#35 - 09.09.1999
Q:	When an outdoor light sensor is not working properly, who should be informed? All users? Those on the rooms where the calculation of the light flow depends on the malfunctioning sensor? Who? [9:U8]
A:	The following persons should be informed: 1) the facility manager and 2) the users who occupy a room where the calculation of the light flow depends on the sensor with the malfunction.

#36 - 09.09.1999
Q:	In 9:U1, what is the meaning of "...nothing else is desired ..."? Does this "nothing else" means "no more additional illumination"?
A:	No, the illumination can also be decreased. The user can decide to have unsafe illumination in his room.

#37 - 09.09.1999
Q:	What happens when a user turns off any light using the push-buttons? How are they turned on again? [6:P8.2,6:P14.3]
A:	The next push on a push button (5:P14.3(ii)), or the detection of occupancy according 9:P27.13 after a certain delay time (defined by the facility manager), or the detection of a future occupancy according to 9:P27.14 will turn them on.

#38 - 09.09.1999
Q:	Why will each ceiling light group be controlled by several push-buttons? Why not just one? [6:P8.2,6:P14.3]
A:	This is a property of the already existing installation.

#39 - 12.10.1999
Q:	9:U9(i), (ii) Does (i) imply an ability to set each of the ceiling light groups on or off ? The setting of (i) could then conflict with the third attribute definition of the chosen light scene (wall, window, both). In case of conflict, which one of the two should prevail ?
A:	Each of the ceiling light groups can be set by the user on or off by using the control panel. This has preference over the attribute definition of the chosen light scene (wall, window, both).

#40 - 12.10.1999
Q:	9:U5, 13:T3(light-scene): For each room is it possible to define any number of light-scenes, each given a unique name. User of that room may then select any of these as the "chosen light scene"?
A:	A limited number of three light scenes is sufficient in this case. Each has a unique name, given by the user. Any of it can be selected by the user as the "chosen light scene".

#41 - 12.10.1999
Q:	5:P8, 9:U2 Ideally, if a room user has manually set the light groups and/ or adjusted their luminescence using the dimmer(s), then these lights should not be controlled by the control system until the room is un-occupied for more that T1 minutes. However, there seems to be no way for the system to completely sense that the manual over-ride has been exercised by the user (ie. adjustment of the dimmers). So it seems that the manual adjustment done by the user will be over-ridden by the chosen light scene, when the system checks the luminescence of this room the next time, based on its monitoring frequency. This may encourage the user to define a chosen light scene instead, suitable to his/ her requirements, however. Is this understanding correct?
A:	The control system is able to sense all manual settings: a) Switching on/off the light groups is possible directly by use of the push buttons or indirectly by the control system. In either case the control system is aware of the current setting (see "status line" of the dimmable light). b) Dimming the light is not possible directly. There is no way to bypass the control system.

#42 - 02.11.1999
Q:	Referring to 9:U1, 9:U9, 9:U13 and the answers to Q36 and Q2, I still can't decide what "nothing else is desired" actually means. As far as I read U1, it says: U1 If a user occupies a room, there must be safe lighting (>14lux) unless the user wants something else. Q36 specifically states that this "something else" can be as dark or as light as the user wishes. But this happens only if there is some chosen light scene (whatever its desired lighting characteristics). Naively, I could assume that both the user-settable light scenes (at least three, Q40) and the default light scene indicate user wishes about the lighting. In that case, user wishes will always override the "safe lighting" requirement. Is that the intended meaning? Or is the default litght scene a way of indicating there is no user wish and should I read U1 as: U1 If a person occupies a room, there has to be safe lighting unless a specific light scene has been chosen; this means that when the default scene is established (ie. through U4) and the room is occupied, there must be safe lighting. When the room is occupied and some light scene has been chosen by the user, the lighting must be set according to that scene. Hopefully this will finally pin down U1 exactly, it seems to be one of the most problematical of all the requirements.
A:	We take over your proposal with some minor changes. So we get a new version of requirement U1: U1 If a person occupies a room, there has to be safe illumination unless a specific light scene has been chosen or the ceiling light groups are set manually. This means that when the default scene is established (ie. through U4) and the room is occupied, there must be safe illumination. When the room is occupied and some light scene has been chosen by the user, the lighting must be set according to that scene.

#43 - 10.11.1999
Q:	I think, it would be more practical that the default light scene is decided by the control system (for example, one ceiling light group on and with safe illumination) but not set by the users (see 9:U6 and 9:U9(ii) ), because the default light scene is only used for the case that a room is reoccupied after T1 minutes.
A:	Of course, this would be another reasonable variant. But in order to keep the changes to the problem description as minimal as possible, the corresponding requirements should not be modified.

#44 - 15.11.1999
Q:	Does connected in 5:P6, 6:P15, 13:"staircase" mean the same as adjacent in 5:P7, 5:P13, 6:P16, 6:F2 ?
A:	Rooms or hallways are adjacent, if they are neighboured. They are connected, if they have at least one common door. Obviously, connection implies adjacency.

#45 - 15.11.1999
Q:	9:U8 : How is the user of the room informed? With an indicator light on the room's control panel?
A:	Yes.

#46 - 15.11.1999
Q:	9:U11 : Is that as movable as a telephone with a cord or as movable as a cordless telephone? Are you trying to say that the control panel has a cord to connect it to the wall? Are you trying to say that the control panel works by a cordless mechanism?
A:	The control panel is as movable as a telephone with a cord.

#47 - 15.11.1999
Q:	Is the "desired" light setting in 10:FM1 the chosen light setting? What is the relationship between a light scene, and a light setting?
A:	(Chosen) light scenes are set by the user or facility manager. (Desired) light settings are determined by the control system, thus they occasionally depend on the light scenes.

#48 - 15.11.1999
Q:	10:FM6 : What happens if he or she tries to turn of the ceiling light group in an occupied room or hallway section? What takes precedence, safety or the direct order?
A:	In the case of an occupied room or hallway section, he may not turn off the ceiling light groups.

#49 - 15.11.1999
Q:	What are the unusual conditions in 10:FM10? What are the differences between malfunctions and unusual conditions?
A:	A malfunction is the incorrect behaviour of a control system device (see 13:"malfunction"), e.g. a sensor does not return correct values. The distinction between unusual condition and normal operation must be defined individually for each possible situation. For example, the range of un-/reasonable sensor values or the interval of un-/acceptable user inputs. A complete list of such situations should be suggested by the system developer.

#50 - 15.11.1999
Q:	10:NF1 : Even if it causes unsafe lighting?
A:	Yes. Light scenes have always priority over safety.

#51 - 15.11.1999
Q:	10:NF1 and 10:NF2 can contradict each other.
A:	There seems to be no obvious contradiction, because setting the default light scene does not directly affect the value returned by the outdoor light sensor. However, if there will turn out any indirect contradiction, NF2 should get the higher priority.

#52 - 15.11.1999
Q:	The definitions of luminary and toggle are missing in the "Dictionary of Terms" 12:T3.
A:	luminary a light emitting device. toggle change the state of a ceiling light group from "off" to "on", or from "on" to "off".

#53 - 10.12.1999
Q:	I have several questions relating to the outdoor light sensor (problem description pages 7,13) and the determination of how much light is in each room and hallway section. The problem description 10:FM1 in particular and also 10:NF1 and 10:NF2 indicate that the OLS should be used to determine the amount of light in the room. There are have been a number of questions regarding this point, (Q6, Q17) extending the light transmission even into the hallway. I cannot find where the transfer function is specified (i.e., given a reading of the OLS, how much light is actually in the room or in the hallway section). I also don't see how to come up with this transfer function without a significant amount of information. For example: Is the glass in the windows tinted or not? If it is tinted, how does this effect light transmission? How big are the windows? How many windows does each room have (this is not entirely clear from Figure 1 on page 4)? Are there blinds in the offices? In that case, the light transmission will be greatly affected by whether or not the user has opened or closed the blinds (and no sensors are included to tell if this is the case). Another example is for the hallway: suppose that it is a bright sunny day and the light is shining directly through the window in the office into the hallway. This condition will create a brighter illumination in the hallway than the same day where the light does not shine exactly through the door (i.e., the same orientation, but the window and door do not line up with the light). Take, for example, O425 verses O423 in the 4:F1 (assuming the sun is shining exactly from the West).
A:	In fact, the problem description does not contain any statements about the transfer functions between the outdoor light sensors (OLSs) and the indoor illuminances. This is because the system developers should provide these functions. For the case study, it is sufficient to give a generic specification of the transfer functions, whose actual parameters could be adjusted during the system installation time on the basis of concrete measurements. What you should also know is that rooms have no blinds (neither automatically nor manually driven). This means, that the transfer functions do not depend on (unrecognizable) user interactions. Note, that the dependence between OLSs and rooms also determines which control panel has to indicate which OLS malfunction (see 9:U8 and Q35). A possible dependence relation between OLSs and rooms is suggested below. ols1 o435, o433, o431, o429, m427 ols2 cl426, o424, cl422, ols3 o419, o417, o415, o421, cl422 ols4 cl418, o416, o414, o412 ols5 m427, o425, o423, o421, cl411 ols6 o412, cl410

#54 - 10.12.1999
Q:	Given the issues of Q53, is it possible to assume that each room and hallway section has a light sensor that gives how much light (in lux) is in the room? These sensors are relatively inexpensive so I think that this is a reasonable assumption.
A:	In order to keep additional installations as few as possible, the solution with transfer functions should be prefered.

#55 - 13.12.1999
Q:	5:P8.2, 5:P14.2: Are the push buttons of a ceiling light group or a hallway ceiling light group visible to the control system, i.e. has the control system that will be developed to guarantee the behavior described in the P8.2 and P14.2, if a push button is pushed or are these properties of the pre-installed system?
A:	These are properties of the pre-installed system.

#56 - 13.12.1999
Q:	5:P8.2, 5:P14.2: If the properties asked for in question Q55 are properties of the pre-installed system, in which way can the control system switch on and off a ceiling light group or a hallway ceiling light group? Note that it is only said that a dimmable light has a pulse. Is each ceiling light group in an office and in the other kinds of rooms a dimmable light? A hallway ceiling light group seems to be no dimmable light; nevertheless, is there a pulse to control a hallway ceiling light group by the control system?
A:	Yes, each ceiling light group in an office and the other kinds of rooms is a dimmable light and contains a pulse. Also each hallway ceiling light group contains such a pulse, but it is not dimmable.

#57 - 13.12.1999
Q:	11:NF9, Q45, 7:T2: In which way can the system issues warnings? Using also the indicator light of the control panel? Is there also such an indicator light on the facility manager control panel? Indicator light is obviously a newly introduced actuator: what are its characteristics similar to Table 2? How long should the indicator light be on? Can a user switch off an indicator light?
A:	There are the following indicator lights on the control panel: each room control panel has an indicator light to issue warnings concerning unreasonable inputs each room control panel has an indicator light to issue malfunctions of the sensors and actuators used in this room the facility manager control panel has an indicator light to issue warnings concerning unreasonable inputs the facility manager control panel has for each room, each hallway section, and each staircase a separate indicator light to issue malfunctions of the sensors and actuators used in this area The characteristics of an indicator light corresponds with the characteristics of the actuator control system is active. An indicator light should be on after an unreasonable input for at least 1 second and for at most 5 seconds. a malfunction for at least 10 seconds and for at most 24 hours. A user can not switch off an indicator light.

#58 - 13.12.1999
Q:	7:T2 (dimmer): The dimmer has a range of 0-100%, but only the values 0% and 10-100% are explained. What is the meanning of the values 1-9%?
A:	For 1-9% the dimmer is off, too.

#59 - 13.12.1999
Q:	What are the initial values of the values that can be entered by a person? What are the initial values for the actuators?
A:	The system developer should suggest reasonable initial values.

#60 - 13.12.1999
Q:	6:P14: How many push buttons are there in the several hallway sections?
A:	In each hallway section there are 3 push buttons.

#61 - 13.12.1999
Q:	9:U9(i), Q39: What does "set" in U9(i) include? Only switching on and off the ceiling light groups as said in the answer of question Q39 or should it also be possible to set the dimmer by using the control panel?
A:	The control panel should include a possibility to set the dimmer of each ceiling light group.

#62 - 13.12.1999
Q:	9:U9, Q39: Using the control panel, a specific light scene can be chosen and it is possible to set the ceiling light groups directly. According to the answer of Q39 the second case has preference, but how can the control system determine, that the ceiling light groups are set directly and not by a light scene. Therefore, I think the control panel has to provide a further possibility by which it can be selected whether the ceiling light groups are set through a light scene or through the direct settings.
A:	The control panel should include such a possibility.

#63 - 13.12.1999
Q:	10:FM6: I assume that the facility manager can turn off the ceiling light groups by using his control panel, is this correct?
A:	Your assumption is correct!

#64 - 13.12.1999
Q:	9:U8: Should a user only be informed if an outdoor light sensor or the motion detector of a room does nor work correctly or should he be informed if any sensor or actuator concerning the room he occupies has a malfunction?
A:	A user should only be informed, if any sensor or actuator concerning his room has a malfunction.

#65 - 13.12.1999
Q:	9:U8, 10:FM7: Should user and facility manager also be informed when there is no longer a malfunction?
A:	This would be reasonable, but it is not required.

#66 - 13.12.1999
Q:	10:NF2 states that "the default light scene for all rooms is that all ceiling light groups are on". But the definition of a light scene in 13:T3 does not include any possibility to specify switched-on lights. So how should NF2 be realized?
A:	You can use the setting "both" together with a very high desired ambient light level.

#67 - 13.12.1999
Q:	There are two locations where the default light scene is defined: in 9:U6 by the user control panel and in 10:NF2. But which of these is the actual default light scene, that should be used? Probably, the default light scene of NF2 should have a higher priority?
A:	Yes. It should.

#68 - 14.12.1999
Q:	A dimmable light, described in 8:S2.10, is defined in 12:T3 as a "luminary that can be dimmed"; and a ceiling light group in an office is a luminary (12:T3) and it can be dimmed (5:P8.3). Is a ceiling light group in an office an instance of a dimmable light, in the sense of Section 2.10? How about a hallway ceiling light group, which is not described as dimmable in 5:P14 (but is not described as "not dimmable" either)? Is a ceiling light group a single controllable unit, or a collection of controllable units?
A:	Ceiling light groups in offices are instances of dimmable light. Each office has according 5:P8.2 two ceiling light groups. The luminaries inside each ceiling light group can only be turned on or off and additionally dimmed as a group. But the two ceiling light groups can be adressed separately. Hallway ceiling light groups can not be dimmed.

#69 - 14.12.1999
Q:	8:F3: What is represented by the railroad crossing icon (circle with X) in the lower right of the diagram? What is the railroad crossing icon's relation to the dimmable light, to which it is connected?
A:	The railroad crossing icon represents here the luminaries inside a ceiling light group.

#70 - 14.12.1999
Q:	8:F3: What is the "item" sticking out of the bottom of box labeled "dimmable light"?
A:	It is the ground connection.

#71 - 14.12.1999
Q:	In 8:F3 "Dimmable Light", what is "phase" -- is it a status line for the push button?
A:	Yes.

#72 - 14.12.1999
Q:	8:P19 states that if the "control system active" signal is not sent every 60s, the dimmable light switches to fail safe mode. Is this a requirement that the control system must fulfill (i.e. the control system must switch the dimmable light to fail safe mode), or a property of a dimmable light that the control system can take advantage of? Can the control system put a dimmable light into fail safe mode?
A:	It is a requirement, i.e., the dimmable light should* switch to fail safe mode, if the control system active signal is missing.*