while this invention is susceptible of embodiment in many different forms , there are shown in the drawing and will be described herein in detail specific embodiments thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated . fig1 illustrates a system 10 which embodies the present invention . in fig1 waterflow conduits c 1 , c 2 . . . cn of a type that might be found in a building fire alarm system are each connected to a respective sprinkler head ( not shown ). as is conventional , in the presence of heat , the respective sprinkler head or heads become activated whereupon fluid in each of the respective conduits ci flows under pressure , indicated at f 1 , f 2 . . . fn through the activated sprinkler head to suppress the fire in the respective region . fig1 also illustrates a plurality of flow detectors 12 - 1 , 12 - 2 . . . 12 n . each of the flow detectors 12 - i is operatively coupled to a respective conduit ci to detect a fluid flow fi therein . an indication of this fluid flow can be provided at a respective output port , on lines 14 - 1 , 14 - 2 . . . 14 - n in the form of an electrical signal . for example , in a no flow condition , a normally open contact or a normally closed contact closure can be provided with a respective change of state produced by the flow fi . for purposes of maintenance each detector , such as detector 12 - i , has associated with it a respective test unit 20 - i . associated with each respective test unit 20 - i is a pump 22 - i electrically coupled to the respective test unit 20 - i . each of the pumps can draw fluid from and return fluid to the respective conduit c - i to create test flow fit by means of a respective test flow input conduit 24 - i and a respective test flow output conduit 26 - i via an output 14 ′- i . the respective output signal on the line 14 - i can in turn be coupled directly to the respective test unit 20 - i . alternately the output signal can be coupled to a system control unit indicated generally at 16 via an output 14 ′- i . control unit 16 in turn can respond to the detected fluid flow by energizing alarm output devices 16 a . each of the test units 20 - i incorporates a manually operable control element 30 - i . this element might be a multi - position key switch , for example , or a keypad or card reader . using the control element 30 - i the respective test unit 20 - i can be placed into an active state whereupon the respective pump 22 - i will be activated . hence , in the active state , the respective test unit , 20 - i can energize pump 22 - i and produce a flow of fluid fit in the vicinity of the respective flow detector 12 - i . the detector 12 - i will in turn , upon detecting the test flow , output a test signal from its output port on line 14 - i which is in turn sensed by test unit 20 - i . one output from the respective detector 12 - i can be coupled to the respective test unit 20 - i . the other can be directly coupled to the control element 16 as required . a selected test mode can be entered at unit 12 - i by a manual input at the respective control element 30 - i . alternately control unit 16 can issue an appropriate command or commands to the respective test unit . in addition to individually actuating each of the units 20 - i , group testing can be implemented . test units can be coupled together , based on groups of detectors , indicated by signal paths 32 - 1 . . . 32 - n − 1 . in such an instance , the system will support a mode of multiple unit , group , activation . a single control signal , from , for example , element 30 - 1 or control unit 16 can activate test unit 20 - 1 to carry out a selected type of test . this activation can in turn be coupled to test unit 20 - 2 and on to test unit 20 - n , assuming they are in the same group , causing those respective units to carry out the same type of test in response to a single initiating control signal . various types of test unit outputs can be initiated . for example , the respective test unit can actuate the respective pump , for example once a week , for a brief period of time such three hundred milliseconds . in another mode , the respective test unit can be placed into a self - test mode whereupon the respective pump will be energized continuously until the test unit is taken out of that mode . finally , a group test can be carried out wherein when a selected test unit , such as unit 20 - i is activated , those units to which the activated test unit is coupled , via signals 32 - i will also be tested in the same fashion . for example , in group test , a continuous test output can , in a preferred embodiment , be produced until the unit is released manually . fig2 illustrates in greater detail , in block diagram form , the structure of respective test units such as 20 - i and 20 - i + 1 . elements in fig2 which are common with those in fig1 have been assigned a corresponding identification numeral . the following discussion of test unit 20 - i is applicable to the remaining test units so only unit 20 - i needs to be discussed . the test unit 20 - i includes a programmable processor , such as a microprocessor , 40 - i . an input port of the processor 40 - i , indicated generally at 42 - i , is coupled to the output port of the respective flow detector 12 - i . an output port 44 - i is coupled to the respective water pump 22 - i . output drive circuitry , which could be implemented as either a relay or a solid state switch , indicated generally at 46 - i provides interface circuitry between processor 40 - i and waterpump 22 - i . coupled to processor 40 - i is a storage unit 48 - i which could be integral therewith wherein instructions executable by processor 40 - i are stored . storage units can be implemented as ram , rom , eeprom or the like without limitation . execution of these instructions enables processor 40 - i to carry out different processing sequences based on the setting of input control element 30 - i , or , based on signals received from another test unit on communication lines 32 -( i − 1 ). an optical isolator 50 - i can be interposed between the communication lines 32 -( i − 1 ) and processor 40 - i for isolation purposes . additionally , output drive circuitry 52 - i can be provided between processor 40 - i and output communication lines 32 - i . this circuitry is in turn coupled to test unit 20 -( i + 1 ). it will be understood that a variety of control programs can be loaded into the storage unit or memory 48 - i without departing from the spirit and scope of the present invention . however , irrespective of how implemented , such control programs will enable the respective test unit 20 - i to energize the respective pump 22 - i and receive or sense signals from the respective detector 12 - i in accordance with the selected operational or test mode . fig3 illustrates an alternate implementation , in block diagram form , of system 10 of fig1 . elements in fig3 which are common with those in fig1 or 2 have been assigned a corresponding identification number . unlike the system of fig2 in the system of fig3 test units such as 20 ′ i and 20 ′ i + 1 , when in a common group , can be coupled together using a two wire interconnect 33 - i . in each instance , a respective processor such as 40 ′- i and 40 ′- i + 1 has a group test input port connected to the two wire interconnect system 33 - i . in this embodiment , all members of one group would be coupled to interconnect 33 - i as illustrated in fig3 . setting a respective test unit 20 - i in the group into a group test mode using manual input 30 - i will cause an appropriate signal to be transmitted via the two wire interconnect 33 - i to all group members . as a result , group members will carry out an essentially simultaneous group test of the respective water flow detector , such as the detector 12 - i . it will be understood that as an alternate to initiating the group test mode using the manual input device 30 - i , a command can be initiated from the control element 16 to carry out a group test . in this instance , a specific group would be identified by the control element 16 . the test units 20 - i in each group would recognize that they are part of the specified group for carrying out the required test . from the foregoing , it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention . it is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred . it is , of course , intended to cover by the appended claims all such modifications as fall within the scope of the claims .