Electrical connector

1. An electrical connector comprising:

an insulating housing;

contacts that are accommodated in this housing; and

a retainer that is inserted from the front surface of the housing, and that is locked to the housing in a temporary locking position that allows the insertion of the contacts into the housing and in a main locking position that ensures that the contacts are prevented from slipping out of the housing,

the retainer having a front plate that has contact passage holes, and locking arms that extend rearward from the upper and lower ends of the front plate, wherein

the retainer comprises a strip that protrudes rearward from the center of the front plate on a back surface thereof, and also has a recessed groove that extends in the center of the front plate on a front surface thereof and in a position corresponding to the strip, and

the housing has a recessed groove that mates with the strip when the retainer is in the main locking position.

2. The electrical connector of claim 1 , wherein the contacts are accommodated in contact cavities, the rows being separated by a central partition wall and the cavities in each row being separated by cavity partition walls.

3. The electrical connector of claim 2 , wherein the recessed groove in the housing is defined by the cavity partition walls protruding further forward than the central partition wall.

4. The electrical connector of claim 1 , wherein the strip extends in the direction of length of the retainer.

5. An electrical connector, comprising:

an insulating housing having a plurality of contacts accommodated in contact accommodating cavities, the housing having a recessed groove formed inside the housing between the contact accommodating cavities; and

a retainer that is inserted from a front surface of the housing, the retainer being moveable between a temporary locking position that allows insertion of the contacts into the housing and a main locking position that locks the contacts in the housing, the retainer having a front plate with contact passage holes, the front plate having locking arms extending rearward from upper and lower ends thereof and a strip that protrudes rearward from a back surface thereof that mates with the recessed groove of the housing in the main locking position.

6. The electrical connector of claim 5 , wherein the retainer includes a recessed groove formed on a front surface of the front plate in a position corresponding to the strip.

7. The electrical connector of claim 6 , wherein adjacent contact accommodating cavities are separated by cavity partition walls and a central partition wall divides the contact accommodating cavities into upper and lower rows.

8. The electrical connector of claim 7 , wherein the recessed groove in the housing is defined by the cavity partition walls protruding further forward than the central partition wall.

9. The electrical connector of claim 6 , wherein the strip extends along a direction of length and has a fixed height along the direction of length.

10. The electrical connector of claim 9 , wherein the recessed groove of the retainer extends along the direction of length has a fixed depth along the direction of length.

11. The electrical connector of claim 10 , wherein the strip and the recessed groove of the retainer are formed in a center of the front plate.

12. The electrical connector of claim 6 , wherein the strip and the recessed groove of the retainer have a trapezoidal cross-sectional shape that is tapered towards a rear thereof.