Why are the Agilent 8761B SPDT Coaxial Switches not listed in the "Agilent 34945A, L4445A and L4490A/L4491A Configuration Guide"?
The Agilent 8761B coaxial SPDT switches utilize a two-terminal dc connection for position control. Switch path selection is achieved and toggled by reversal of the DC polarity across these coil terminals. The following excerpt from the "Agilent 8761A/B Microwave Switches Technical Overview":
To change the state of the switch requires a reversal of the voltage polarity for at least 20 milliseconds.
8761B Coil Connection Schematic (NOT supported by the 34940A / L4445A / L4490A / L4491A)4490A / L4491A)
Conversely, for other ‘supported’ coaxial switches the 34940A / L4445A / L4990A / L4491A achieve switch control by providing a constant positive dc supply (typically +28Vdc) to the positive common coil input connection. Supported SPDT switches, such as the Agilent N1810 Family, then employ a dual coil control where the path selection is engaged by closing coil’s ground connection. The following excerpt from the "Agilent N1810/1 /2 Coaxial Switches Technical Overview":
There are two positions for the N181x family of switches. Standard switching is accomplished by applying the supply voltage to pin 5 (+V) and grounding either pin 4 (A) or pin 3 (B) to actuate the mechanism to the desired state.
N1810TL Coil Connection Schematic (supported by the 34940A / L4445A / L4490A / L4491A)
Additionally, the Agilent 8761A SPDT coaxial switch is not supported by the 34940A / L4445A / L4490A / L4491A. The Agilent 8761A employs dc polarity reversal equivalent to the 8761B but differs from the 8761B in that the coil voltage requirements are 15Vdc.