StudioTech M46-00180 manual Advanced Configuration, Auto Terminate Disable

Advanced

Configuration

Four DIP switches are provided on the Model 46’s back panel. They allow the two interfaces to be configured for several ad- vanced operating modes. Refer to Figure

7 for a detailed view of these DIP switches. The available modes include auto termi- nate disable, auto null button operation, refresh disable, and factory test.

Figure 7. Detail of back panel showing the Advanced Mode DIP switches

Auto Terminate Disable

The auto terminate function is designed to ensure that each 2-wire-to-4-wire interface circuit remains stable under most oper- ating conditions. Specifically, 200 ohm impedances are automatically applied to both pins 2 and 3 of a Model 46 2-wire party-line interface when that interface is configured for external power and no ex- ternal source of intercom power is detect- ed on pins 2 or 3. This function is directly compatible with RTS TW-series intercom applications in which the three conductors of a cable support both DC power and two channels of audio. It’s also compatible in situations where all three conductors of a Clear-Com single-channel intercom circuit

are connected to the Model 46. In this lat- ter case only one of the Model 46’s audio channels will be used.

There may be situations where it’s nec- essary for the two channels associated with each Model 46 interface be used with separate 2-wire party-line circuits. An example of this might be where two “loops” of single-channel belt packs, such as units from Clear-Com, need to be connected. Adapter cables as shown in Figure 2 would be used. In this case the intercom circuit’s DC power will not be connected to the Model 46, but only to the user devices. In this scenario, a DC volt- age won’t be present on pin 2 or pin 3. Another example of this might be where adapter boxes with DC blocking are used to interconnect intercom circuits with the Model 46. In both these cases a DC volt- age won’t be present on either pin 2 or 3 and the Model 46 will automatically apply 200 ohm terminations. In both these cases the termination will be in error and will re- sult in incorrect audio levels due a double- termination condition.

To prevent this problem the auto termi- nate function can be disabled. When DIP switch 1 is in its off (down) position the auto terminate function is active. When switch 1 is in its on (up) position the auto terminate function associated with each interface is disabled. Repeating for clarity, the auto terminate disable function applies to both interfaces 1 and 2. With the auto terminate function disabled the two 46 interfaces, when set for external power, will operate normally with the exception that pins 2 and 3 will never be terminated by the Model 46’s circuitry.

Issue 2, September 2007	Model 46 User Guide
Page 18	Studio Technologies, Inc.