Synchronization Notes:

• The official clock synchronization pulse is sent directly to all receivers, regardless of their audio settings or other status. As long as a receiver is tuned to the CRC's DVB carrier, they will receive the closure at the common time.
• The official update time is xx:54:30 every hour.
• The pulse is exactly one second in length. The closure is normally open, and is closed for the duration of the pulse. It is not closed at any other time by anyone.
• The closure is labeled "CLOSURE 1" directly on the back of the Unity 4000 receiver. It has two terminals, labeled "+" and "-"
• The closure is not a dry relay.  It is an open-collector transistor output.
  Thus, it is polarity-sensitive.
• You may need either an external pull-up resistor on the collector ("+" terminal) or an external power supply with a small relay (a "reed" relay, for example) to interface properly with your automation system.
• When held closed during the pulse, the operating resistance of the transistor output has been measured at about 110 ohms. This needs to be considered in any external circuitry in order to not overload the transistor output. The transistor is capable of carrying only a small amount of current (less than 100mA), so do not overdrive it.