# What is purpose of this resistor

#### Englandfengyu

Joined Jul 4, 2021
4
I recent installed a taxi meter to my touran . And I watched the guy from beginning to finish . And I don't understand the use of that resistor . The resistor is used between a pulse wire and 12 v supply wire . Any answer very appreciated . Thanks

#### Attachments

• 1.8 MB Views: 41

#### AlbertHall

Joined Jun 4, 2014
12,293
It looks like a pull-up resistor for an open collector or mechanical switch. The wiki below refers to open collector where the transistor is used as a switch but the same system applies to a mechanical switch as well - relay, cam switch, or push button.
https://en.wikipedia.org/wiki/Open_collector

#### Ian0

Joined Aug 7, 2020
8,944
That must be the resistor that keeps the fare clocking up when you are stationary in traffic!

#### MisterBill2

Joined Jan 23, 2018
16,550
It looks like a pull-up resistor for an open collector or mechanical switch. The wiki below refers to open collector where the transistor is used as a switch but the same system applies to a mechanical switch as well - relay, cam switch, or push button.
https://en.wikipedia.org/wiki/Open_collector
A.H. is correct!!! That is a pull-up resistor. It limits the current which is a very important function. The statement in post #3 is justa random guess that is incorrect. Standing time is added by an internal clock when motion pulses are not detected.

#### Englandfengyu

Joined Jul 4, 2021
4
It looks like a pull-up resistor for an open collector or mechanical switch. The wiki below refers to open collector where the transistor is used as a switch but the same system applies to a mechanical switch as well - relay, cam switch, or push button.
https://en.wikipedia.org/wiki/Open_collector
Thank you very much

#### Englandfengyu

Joined Jul 4, 2021
4
A.H. is correct!!! That is a pull-up resistor. It limits the current which is a very important function. The statement in post #3 is justa random guess that is incorrect. Standing time is added by an internal clock when motion pulses are not detected.
Thank you very much . Limits the current ? How ? I thought it just pull source to known state .

#### Englandfengyu

Joined Jul 4, 2021
4
That must be the resistor that keeps the fare clocking up when you are stationary in traffic!
good guess thank you very much

#### Ian0

Joined Aug 7, 2020
8,944