Tech Notes
Remoting the Status Indicator on Older DXR and DXP G.722 Digital Audio Codecs
On all current DXP.1 and DXR.1 G.722 codecs, there is an 1/8” phone jack labelled “Contact Closure Ready.” This connection is provided for people who want to control remote indicators or unattended tape machines when the codec READY light comes on. (The READY light indicates the presence of valid G.722 data at the input of the decoder side of the codec.)
On older DXR and DXPs, the connection can be made via an uncommitted “open drain” pin available from the data connector of most units. In essence, this pin is of high impedance when the codec ready light is off. When the ready light comes on, the pin becomes low impedance to ground (about 75 ohms) and can sink about 25 mA at 5V. This should be enough to engage a relay to provide a contact closure or even enough to trigger some equipment directly.
On DXRs with two data connectors (V.35 and X.21), the open drain connection is found on the DB-15 connector on the rear panel on Pin 1. Ground is available on Pin 8. If your DXR has only a V.35 connector, you may make these same connections to the DB15 footprint on the main PC board inside the DXR.
On DXPs with X.21 connectors, the open drain connection is found on Pin 15 and Pin 8 is still ground. DXPs with a V.35 connector may be connected to the DB15 footprint inside the unit on the main PC board, still using Pin 15 and Pin 8.
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