What are the meanings of a series of symbols such as NC, NO, COM and PUSH?

The meaning of each symbol in the entrance guard:

Push: refers to short circuit to ground to unlock;

PUSH+: refers to the short-circuit positive pole unlocking, and the output of some access controllers is instantaneous 12V, which is connected to this terminal;

NC: means normally closed;

No: normally open;

COM: refers to the public terminal;

LOCK+: refers to the L+connected to the intercom terminal;

LOCK-: means L- connected to the intercom terminal.

Access control refers to the forbidden authority of "door" and is a precaution against "door". The "doors" here, in a broad sense, include all kinds of passable passages, including doors for people and vehicles. Therefore, access control includes vehicle access control. In the application of parking lot management, vehicle access control is an important means of vehicle management.

It involves many new technologies such as electronics, machinery, optics, computer technology, communication technology and biotechnology. It is an effective measure to solve the entrance and exit problems of important departments and realize safety management. Suitable for all kinds of security departments, such as banks, hotels, computer rooms, armories, confidential rooms, offices, intelligent communities, factories and so on.

Extended data:

1, general access control:

Advantages: convenient operation, no need to carry cards; Low cost.

Disadvantages: easy to leak, poor security; No entry and exit records; Can only control one direction. Keys are prone to damage and malfunction.

2. Out-of-order keyboard access control (the numbers on the keyboard are not fixed and will change automatically from time to time):

Advantages: convenient operation, no need to carry a card, and slightly higher safety factor.

Disadvantages: the password is easy to leak, and the security is still not high; No entry and exit records; Can only control one direction. High cost. Keys are prone to damage and malfunction.

Baidu Encyclopedia-Access Control