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Chapter 7 Plug-in Modules
44477A Form-C Relay Module
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7
44477A Form-C Relay Module
The Agilent 44477A consists of seven independent, break-before-make,
SPDT Form-C latching relays (one contact normally open, one contact
normally closed).
The 44477A can be used for signal switching or power applications
(250V, 2A). Additionally, this module is ideally suited for driving remote
RF, coaxial, and microwave devices such as the Agilent 8761, 8762A/B/C,
8763B/C, and 8764B/C switches or programmable step attenuators like
the 876xx series.
You can use the 3499A/B/C +5 V power supply available on the module or
provide an external supply to use as pull-ups on either the NO or NC
paths.
The 3499A/B/C identifies this module as a 44471A on the front-panel
display. Changing the state of channels other than channels 00 through
06 does not generate an error, but has no effect.
Specifications for the 44477A are given on page 345.
44477A Simplified Schematic
A simplified schematic is given on the next page. The 44477A consists of
seven independent Form-C relays (K901-K907) which are numbered as
channels 00 through 06. Closing a channel (relay) will connect the
normally open (NO) contact to the common port (C). After power-on or a
reset, the Form C relays on the 44477A have their normally open (NO)
contacts open and normally closed (NC) contacts closed.
Each relay circuit has mounting holes (JM901 - JM914) used to add a
pull-up resistor from the NO (normally open) and/or NC (normally
closed) contacts to the +5V power supply. Also, there are mounting holes
(JM921 and JM922) at the +5V supply for the addition of a protection
resistor or inductor if the internal supply is to be used. If the internal
supply is not used, an external power supply can be applied through the
screw terminal block via the “H” terminal. The addition of pull-up
resistors can be useful when driving logic circuits where the common (C)
terminal is connected to ground and used to pull either the NO or the NC
line low.
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