M468 — High Level Switcher

The M468 Switcher module contains an 8 input to 1 output relay switcher. The switcher may be operated directly by depressing the momentary pushbuttons on the front panel or they may be remotely operated from a separate remote panel.

Depressing SWl grounds the lower side of Kl which will energize,closing its contacts. The base of 01 is switched to two diode ' drops above ground via CR2 and CR18. Since the emitter is 3.3 volts above ground, 01 will turn off removing the ground return path for the hold circuit of the remaining relays. When SWl returns to its normal position (OFF), Ol,which turns on within several microseconds,provides the ground return path via the Kl holding contacts and therefore Kl remains energized.

To prevent more than one relay from being energized at a time, the ground control line is looped through each pushbutton switch.

The self-latching capability may be removed by disconnecting the ground return jumper between module connector pins U and 16. In addition, the cancel function is brought out at pin T to permit expanding the switcher size beyond 8 X 1.

Audio input #1 appearing 'at pins 1 and A is switched onto the output buss (pins 10 and L) via two sets of KI ts contacts. Depending upon the nature of the switcher built, isolation resistors may be required. These are normally not supplied, but may be installed when necessary.

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M 468

REPLACEABLE