StudioTech 233 manual External Power Input

intercom channels. In addition, the inter- com line can provide the DC power re- quired to operate the Model 233’s circuitry.

An intercom line is connected to the Model 233 by way of a 3-pin female XLR- type connector which is located on the back panel. The mating connector (male) should be wired so that common is on pin 1, DC with channel 1 audio is on pin 2, and channel 2 audio is on pin 3. With single-channel intercom lines common is on pin 1, DC power is on pin 2, and audio is connected to pin 3.

The Model 233’s intercom interface is directly compatible with broadcast and production party-line intercom lines as- sociated with systems from manufactures such as RTS and Clear-Com. Intercom lines associated with other systems should be equally compatible. RTS TW series systems are normally interfaced using 3-pin XLR-type connectors. These connectors are wired with common on pin 1, DC power and channel 1 audio on pin 2, and channel 2 audio on pin 3. With many Clear-Com systems, common is on pin 1, DC power is provided on pin 2, and audio is provided on pin 3.

The DC power supplied by the connected intercom line is generally sufficient to operate the Model 233’s circuitry. The acceptable input range is 24 to 32 volts, with a required current of 125 milliam- peres. Note that the specified input volt- age is given when measured directly at the Model 233’s intercom input connec- tor (with the connector terminated on the Model 233) and not at the source of the intercom system’s power.

External Power Input

An external source of 24 volt DC power can be connected to the Model 233 by way of a 2.1 x 5.5 mm coaxial power jack which is located on the back panel of the unit. The center pin of the jack is the positive

(+)connection. While the requirement for the external source is nominally 24 volts, correct operation will take place over a 20 to 30 volt range. The Model 233 requires

90 milliamperes at 24 volts DC for correct operation. Included with each Model 233 is a 24 volt DC external power supply. The power supply’s DC output cable has been terminated with a Switchcraft® S760K coaxial power plug. This “locking” type of plug correctly mates with the Model 233’s 24 Vdc input jack. The locking feature is im- portant, allowing the external power source to be securely attached to the Model 233.

As previously discussed in this user guide, an intercom line connected to the Model 233 can serve as the unit’s power source. Alternately, an external 24 volt DC source can be connected. For redundancy, the in- tercom line and the external source can be connected at the same time. If one of them becomes inoperative the remaining source will provide power for the Model 233.

The Model 233’s circuitry establishes the priority in which the unit draws its operating power. If an external source of 24 volt DC power is connected, it will always serve as the primary source. This minimizes the im- pact that the unit’s power draw could have on a connected intercom line. If no external source of 24 volt DC is connected then power will be drawn from the intercom line. And, of course, no matter which source is providing power full operation of the inter- com interface can take place.

Issue 1, September 2007	Model 233 User Guide
Page 16	Studio Technologies, Inc.