2.3 Rear Panel Identification and Connectors
9
2.3.3
Event Input
For timing external events based on the GPS-synchronized time, use the Event Input function.
One dedicated event input port is available and equipped with an isolated, BNC female connector.
External events may also be timed from either of the two standard communication ports.
Figure 2.7: Event Input Connector
2.3.4
RS-232 and RS-485 Communication Ports
The Model 1094B has two identical communication ports with RS-232 and RS-485 supported.
The RS-232 port does not use flow control, and RS-485 is transmit only (uses Transmit A and
Transmit B; there is
NO ReceiveA or ReceiveB
). Generally, for RS-232 communications, you will
only need pins 2, 3 and 5 using a null-modem cable. For more information, see Chapter 10, Serial
Communications and Commands.
Figure 2.8: Communication Port Connectors
2.3.5
Form C Relay Contacts
The Model 1094B has one set of Form C relay contacts that have three contact points: Normally
Open (NO), Normally Closed (NC) and Common (COM) as illustrated in Figure 2.9. Contact
functions include Fault, Out of Lock or Programmable Pulse A. Fault, or Out-of Lock, relay
functions are defined when relay is de-energized (e.g. clock powered off). To configure the contact
function, see Section 5.3. For information on how to connect to relay contacts, see Section 9.5; for
specifications, see Section A.4.
Figure 2.9: Relay Contact Connectors
Two examples are cited to clarify the relay operation. The left pin in Figure 2.9 is the Normally
Open (NO) contact to the Common (COM) center pin. The right pin is the Normally Closed (NC)
contact to the Common (COM) center pin.
1. Fault, or Power Off: COM to NC shorted, COM to NO open
2. No Fault and Power ON: COM to NC open, COM to NO shorted
