J. Kissel, V. Sandberg, A. Sevigny

While uncovering the details of E1201027 because of Cheryl's problems (see LHO aLOG 8767), and attempting once again to merge the digital infrastructure for the HAUX and HTTS (see ECR E1300578), I discovered yet another, annoyingly subtle, difference, between these suspensions that has hindered progress: 

- Yes, the HAUX and HTTS are driven by the same coil driver *board,* D1100117, and therefore have the same (switchable) frequency response and output impedance.
- Yes, the HAUX and HTTS drivers have the same coil driver *chassis* drawing, D1100687, which is written on the outside of both chassis.
- Yes, these HAUX and HTTS drivers both have the *ability* to switch their inputs from the DAC to being grounded (think "TEST/COIL" enable in most SUS drivers, but like the Triple Acquisition Driver, there's no external DB9 "TEST" input), and to switch from an "Acquire," high-gain, high-noise mode to a "Run," low-gain, low-noise mode.
- Yes, these HAUX and HTTS both have external input and output spigots for digital Binary Control and Monitoring that would control these switchable features.

HOWEVER, as far as how these chassis are integrated into the rest of the electronics chain is subtly different:
The HAUX drivers ARE digitally controllable, so
- They are connected to Binary input and output chassis
- There is a Contec BIO card in the h1sush2b front-end / IO chassis, and therefore
- There exists digital decoding and control infrastructure to use and handle the switching in the front-end model/code, and
- The MEDM screen to control the switches is fully functional.

The HTTS drivers
- Are NOT hooked up to Binary input and output chassis,
- In order to make the chassis even useable (i.e. the TEST/COIL enable switch must be set to COIL which is not the default), they are INTERNALLY jumpered, without any external indication other than unclearly labeled LEDs being green when the power is on
- In additon, the Run/Acquire filtering has also been INTERNALLY jumpered to be fixed into Run / Low-noise / Low-gain mode,
- A Contec BIO card DOES NOT exist in the h1asc front-end / IO chassis, and therefore
- There is no digital decoding or control authority infrastructure to use and handle the switching in the front-end model/code, and
- The MEDM screen to control the switches exists, but is non-functional.

As far as Vern and I can tell or could find, this fixed configuration of the HTTS drivers, without any BIO chassis or cards is not shown anywhere in the Board drawing D1100117, Chassis drawing D1100687, or the ISC system drawing D1200666.

Oh yeah, and the front face plate color is different (silver vs blue), and the HTTS drivers are labeled "ISC HAM-A Coil Drivers" on the front face plate, as opposed to the HAUX which are just labeled "HAM-A Coil Drivers," both giving the impression from just a superficial glance at the rack and/or chassis that these are different inside. 

*Sigh* Why do we do this to ourselves?