Securitron DT-7 - Manual (Page 5)

PN# 500-11800
Page 5 Rev. C, 02/11
The best way to understand this feature is to use an application as an example. Returning to
our example cited in section 5.3, a security system deactivates at 08:00 each morning and
resecures at 17:00 hrs. Suppose everyone's late to work one day because (for instance) of bad
weather. The facility will be completely unprotected. A better way to operate would be for the
first man to arrive each morning to deactivate the system for the day after which it
automatically reactivates at the end of the day. This is accomplished by connecting dry N.C.
contacts from an external device, to the First Man In terminals (3 and 4). This puts the Prime
Time into First Man In mode. When the unit executes an "on" instruction, the output relay
does not operate until the contacts on 3 and 4 open once. When they open, the relay
follows the "on" program which means energizing in the toggle mode or pulsing 1 second in the
double pulse mode. The First Man In terminals do not have any effect in the single pulse mode.
Subsequent state changes of the contacts on 3 and 4 have no further effect on the relay during
the time the display module is "on". When an "off" instruction executes, the state of the First
Man In terminals again have no effect. They act only to delay the operation of an "on"
instruction.
Returning to our example, let's say the security system consists of an electric lock with digital
keypad for entry. The Prime Time is used in the toggle mode. At night, the display module
reads "off" and power is sent to the electric lock to secure it through the Prime Time's output
relay's N.C. contacts. One pole of the digital keypad's output relay will break power to the
electric lock allowing nighttime entry and the other pole's N.C. contacts connect to the First Man
In terminals of the Prime Time. If someone comes to work at 07:45 am, the Prime Time is still
"off" so they use the digital keypad for entry. When 08:00 comes, the display module switches
to "on" but the operation of the Prime Time output relay is delayed because of the closure
across the First Man In terminals from the keypad. When another man arrives at 08:10,
he also uses the digital keypad and with this first operation (after 8:00 am), the Prime Time's
relay energizes and releases the lock so that all subsequent people can freely use the door
during the day. At 17:00 the unit goes into nighttime mode (off) and deenergizes the relay.
The same results can be obtained in the double pulse mode. The pulse that would occur when
an "on" instruction first executes is delayed until the first man in terminals open.
In addition to avoiding leaving a facility unprotected in the event that employees are late to
arrive, the First Man In feature can eliminate the need for holiday programming.
Returning to our example, if we define a holiday as a day no one comes to work, no one will use
the digital keypad so the electric lock will remain secure all day. When the display module
switches to "off" at the end of the holiday, the lock will simply continue secure and then resume
its normal non-holiday operation the following day. If a particular manager comes to work on
the holiday with this operational concept, he can either leave the lock unsecured all day while he
is there, or change the display module from "on" to "off" by pressing the test button. This action
will resecure the lock. When the 17:00 "off" instruction seeks to execute, the unit will already
be off, so the lock will remain secure during the night as it should.
7. WIRING
Figure 3 shows three "typical" examples of wiring the Prime Time in actual applications. The
first drawing shows the most common use which is simply to switch a device or system on and
off in toggle mode. The second drawing shows use of the pulse mode in the most common
security industry application: that of arming and disarming an alarm panel. Note that there is a
risk in using this set-up in that if the alarm panel is not in the "ready to arm" condition, the
pulse from the Prime Time will not arm the panel. When the next command comes up and the
panel should be disarmed, the panel will interpret the next pulse as another attempt to arm.
Therefore, the Prime Time should only be used to arm and disarm alarm panels in applications
where either they are always "ready to arm" or there is some monitoring which will quickly
detect the fact that there has been a failure to arm.
The third drawing shows the particular application example discussed in section 6 on use of the
First Man In feature with an electric lock and DPDT digital entry keypad. It is intended to display
the general principle as, obviously, other applications are possible. Finally note that the Prime
Time relay is a socket mount. If the relay is damaged from a load short circuit (for instance) it
can be replaced by simply plugging in a new relay. Replacement relays are available from
Securitron or locally from an electric product wholesaler. The relay part number is LY2-DC6 as
manufactured by Omron Electronics. If an Omron part is not available, the equivalent cross