# TTL Switch Control

#### JBizkit

Joined Jul 26, 2019
10
I have a coaxial switch that uses TTL to change the state. Can I use a bench supply to actuate each switch? I am trying to switch each logic condition using +5V for each logic pin I want to turn off and connecting to GND the one I want on. I am looking to check continuity in each position and have had no luck powering up the switch. Could someone please assist?

#### sghioto

Joined Dec 31, 2017
2,363
Follow the Logic Input table. "1" means connect to 5 volts. "0" means connect to ground.
Do you have the + and - 15 volt supplies connected?

#### KeithWalker

Joined Jul 10, 2017
1,786
Yes, you can use the bench supply +5V for a logic 1 on the input, and ground for a 0, as long as you also have the +15v, -15v and grounds all connected. What are you measuring to see if it is working? You should be measuring continuity between each of the J1,J2 and J3 inputs and the J4 output.

#### JBizkit

Joined Jul 26, 2019
10
I am measuring continuity with a hand held meter with the ultimate goal of measuring insertion loss on each path. All supply voltages are connected to the same ground and I am seeing a current draw on the +5V supply, however there is still no connection.

As a sanity check I have verified with a second meter and tried different switches.

#### andrewmm

Joined Feb 25, 2011
1,473
Sanity check.

a) Could it be the switch is AC coupled, i.e. no DC path to meassure with a meter ?
b) ttl is unusual for these switches, the "standard" I have seen is 12V logic switching, suggest you double check data sheet

#### KeithWalker

Joined Jul 10, 2017
1,786
The switch could be AC coupled. What frequency range is it for, or even better, what is the make and model?

#### andrewmm

Joined Feb 25, 2011
1,473
some how, I thought this was for a satellite receiver,
but re reading, it just says BNC,
so it might be 5v TTL. ( satellite ones are 12 V )

appologies