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ZL1ABS > ATV 01.09.09 09:48l 31 Lines 1222 Bytes #999 (0) @ WW
BID : 403340ZL1ABS
Read: DL8SFG GUEST
Subj: 8 Way A/V Switch
Path: DB0FHN<DB0MRW<DB0ERF<OK0NHD<OK0PHL<OK0PCC<OM0PBC<OK0PPL<DB0RES<DK0WUE<
7M3TJZ<ZL2BAU<ZL1AB
Sent: 090901/0831Z @:ZL1AB.#06.NZL.OC #:33493 [AUCKLAND] FBB7.00i $:403340ZL1AB
From: ZL1ABS@ZL1AB.#06.NZL.OC
To : ATV@WW
8 WAY A/V SWITCH
by QUENTIN ZL1QF
The 8 Way A/V switch is used in the ZL1BQ ATV Repeater as well as in some
ATV Home stations. It is made up of three sections, Video, Audio (stereo)
and Display.
The video section accepts the BCD code on the ABC leads from the
thumbwheel switch or encoded rotary switch. The 4051 ic decodes the BCD
and drives one relay at a time via the uPA2003 buffer ic. The relay has a
DPDT changeover contact. Each input can have a 75 Ohm terminating
resistor, if required. A video distribution amplifier can be connected to
the common output.
The audio section is duplicated so that stereo audio switching is
available. The 4051 IC accepts the BCD code on the ABC leads and passes
audio on the selected input to the common output.
The display section accepts the BCD ABC leads and drives a 4511 7 segment
common cathode display driving ic. Series resistors are used to limit the
current to no more than 20mA per segment or less, if the display is a high
efficiency type.
An onboard 7805 5 Volt ic regulator is provided.
PC Boards are available (with the needed 5 Volt Relays ) from Michael
ZL1ABS.
zl1abs@xtra.co.nz
Diagrams to follow by 7 Plus.
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