Cooper TP Workshop Manual_Scant:Layout 1 7/8 ... - Cooper Security

768r/769rPower Input/Output ProtectionThe 0V and 12V input terminals on the main PCB (see Figure 7) and the 12Vsupply from 768r to 769r are protected against reverse connection and shortcircuit. The protection is provided by polyswitches.General3. PLANNINGBefore Installation you should carry out a survey of the site. You need toknow how many and what kind of transmitters will be operating through thereceiver.You also need to assess where the unit(s) must be placed in order tocommunicate with the transmitters successfully. To do this you may need toconduct Signal Strength Tests using a Scantronic 790 hand held signalstrength meter. The 768r/769r units also provide a signal strength testfacility. Note that if you want to carry out signal strength tests you will need toprovide a transmitter. Cooper Security Limited can supply the 746r testtransmitter.A final consideration is the power supply needed for the unit. Note thatneither 768r or 769r contains a power supply.Choosing the Number of Receivers.The number of receivers and expansion cards required depends on thenumber of transmitters being used. To calculate the minimum number ofreceivers needed, add up all the channels being used by the transmitters anddivide by eight. Note that one 768r can support up to three 769rs.ExampleTo show how to calculate the number of receiver units required, here is anexample. A site proposes to use the following types and numbers oftransmitter:• Three single channel 701r pendant transmitters as emergencymedical alarms (requires a total of three channels).• Four dual channel 714r passive infra red detectors (requires atotal of eight channels: alarm plus tamper for each PIR).Adding all the channels required by this collection of transmitters means thatthe installation will be using a minimum of nine channels if the 701r’s shareone channel, or a maximum of 11 channels if each 701r has its own channel.Since each 768r/769r can provide only eight channels the installation willneed two units, giving a maximum capacity of 16 channels. In this exampleyou could use one 768r and one 769r.Issue 1 9 of 28