Method and apparatus for powering and signaling over a single wire pair

• US 5,517,172 A
• Filed: 09/19/1994
• Issued: 05/14/1996
• Est. Priority Date: 09/19/1994
• Status: Expired due to Fees

• Current Assignee: Manfred F. Chiu
• Original Assignee: Manfred F. Chiu
• Inventors: Chiu, Manfred F.
• Primary Examiner(s): Swarthout, Brent A.
• Assistant Examiner(s): TONG, NINA C
• Application Number:
  US08/308,749
• Time in Patent Office: 603 Days
• Field of Search: 340/310.01, 340/310.02, 340/310.03, 340/310.06, 340/310.07, 340/310.08, 340/825.31, 340/825.32, 340/825.34, 340/825.63, 235/449, 235/238
• US Class Current: 340/5.7
• CPC Class Codes: G07C 9/27 with central registration

Abstract

A remote access granting system has a remote access requester that reads an identification code from a magnetic strip on a card and provides a sequence of request signals indicative of logical ones and zeros on separate conductors to a remote access interface. In response to the request signals, the remote access interface pulse modulates a DC voltage signal on a transmission line with a request pulse having a first pulsewidth indicative of a logical one or with a request pulse having a second pulsewidth indicative of a logical zero. A controller interface detects the pulse modulation on the DC voltage signal, demodulates the request pulses, and provides on separate conductors to a controller a first request pulse indicative of a logical one and a second request pulse indicative of a logical zero. The controller determines whether the sequence of request pulses matches a predetermined sequence. If there is a match, the controller provides a lamp enable signal indicative that access is being granted to the controller interface which in turn pulse modulates the DC voltage signal on the transmission line with an access granted signal having an amplitude less than the amplitude of the request pulses and having a frequency different than the frequency of the request pulses. The remote access interface demodulates the access granted signal and provides the lamp enable signal to the remote access requester to enable entry through a security door and to inform the user that such access has been granted.

Claims

1. A remote access granting system comprising:

a remote access requester having a first input for receiving a user-supplied identification code including code data having first and second logic states, having a second input for receiving a first access granted signal, having first and second outputs for providing corresponding first and second access request signals in response to a code datum being in the first and second logic states, respectively, and having a third output for providing an access accepted signal in response to the first access granted signal;

a remote access interface having first and second inputs coupled to the first and second outputs, respectively, of the remote access requester for receiving the corresponding first and second access request signals, having an output for providing the first access granted signal in response to a second access granted signal, and having a bi-directional terminal for receiving a DC voltage signal, for receiving the second access granted signal, for modulating the DC voltage signal with a first modulating signal having a first pulsewidth in response to the first access request signal and for modulating the DC voltage signal with a second modulating signal having a second pulsewidth in response to the second access request signal;

a controller interface having an input for receiving a third access granted signal, having a bi-directional terminal coupled to the bi-directional terminal of the remote access interface for receiving the first and second modulated signals, for providing the DC voltage signal, and for modulating the DC voltage signal with the second access granted signal in response to the third access granted signal, having a first output for supplying a third access request signal in response to the first modulating signal, and having a second output for supplying a fourth access request signal in response to the second modulating signal; and

a controller having first and second inputs coupled to the first and second outputs, respectively, of the controller interface for receiving the third and fourth access request signals, respectively, and having an output coupled to the input of the controller interface for providing the third access granted signal in response to the third and fourth access request signals matching a predetermined code data sequence.

2. The remote access granting system of claim 1 wherein the first access request signal is a pulse signal indicative of the first logic state, the second access request signal is a pulse signal indicative of the second logic state, the third access request signal is a pulse signal indicative of the first logic state, the fourth access request signal is a pulse signal indicative of the second logic state, and the access granted signal is a lamp indicator signal.

3. A remote access communication interface for communicating data over a single transmission line between a remote access requester and a controller, the remote access requester having an input for receiving a first access granted signal and having first and second outputs for providing corresponding first and second access request signals indicative of first and second logic states, respectively, the controller having first and second inputs for receiving third and fourth access request signals indicative of the first and second logic states and having an output for providing a second access granted signal, the remote access communication interface comprising:

a remote access interface having first and second inputs coupled to the first and second outputs, respectively, of the remote access requester for receiving respective first and second access request signals, having an output coupled to the input of the remote access requester for providing the first access granted signal in response to the second access granted signal, and having a bi-directional terminal coupled to the transmission line for receiving a DC voltage signal, for receiving a third access granted signal, for modulating the DC voltage signal with a first modulating signal having a first pulsewidth in response to the first access request signal, and for modulating the DC voltage signal with a second modulating signal having a second pulsewidth in response to the second access request signal; and

a controller interface having a first input coupled to the output of the controller for receiving the second access granted signal, having a bi-directional terminal coupled to the transmission line for receiving the first and second modulating signals, for applying the DC voltage signal to the transmission line, and for forming the third access granted signal by modulating the DC voltage signal in response to the second access granted signal, and having first and second outputs for providing the third and fourth access request signals to the first and second inputs, respectively, of the controller in response to the first and second modulating signals, respectively.

4. The remote access communication interface of claim 3 wherein the first access request signal is a pulse signal indicative of the first logic state, the second access request signal is a pulse signal indicative of the second logic state, the-third access request signal is a pulse signal indicative of the first logic state, the fourth access request signal is a pulse signal indicative of the second logic state.

5. The remote access communication interface of claim 3 wherein, the third access granted signal modulates the DC voltage signal at an amplitude less than the amplitude of the first and second modulating signals and at a frequency different than the frequency of the first and second modulating signals.