Thanks Bob. First quarter 2016 end user net revenues were $8.2 million or 94% of net revenues compared to $7.7 million or 97% of net revenues in the fourth quarter. OEM net revenues grew $493,000 or 6% of net revenues, up from $219,000 or 3% for the fourth quarter of 2015. Net revenues from markets outside of semiconductor tests were $2.6 million or 30% of net revenues compared with $2.7 million or 34% of net revenues in the fourth quarter.
The Company's first quarter gross margin was $4.1 million or 47% as compared with $3.6 million or 46% in the fourth quarter. The improvement in the gross margin was the result of a more favorable absorption of our fixed manufacturing cost, which were relatively unchanged at $1.4 million, but as a percentage of our revenues decreased from 17% in Q4 to 16% in Q1. Partially offsetting this decrease was a slight increase in our consolidated component material cost, which grew from 32.8% in the fourth quarter to 33.8% in the first quarter.
The increase in our consolidated component material cost was the result of an increase in component material costs of our mechanical product segment, which increased from 41% in the fourth quarter of 2015 to 44.3% in the first quarter of 2016. The increase in the Mechanical Products segment's Q1 2016 component material costs was driven by increase in manipulator product sales, which increased from 26% of fourth quarter mechanical product segment sales to 43% of first quarter sales. This increase was partially offset by a reduction in the component material cost in our Electrical Products segment, which declined from 36.2% in the fourth quarter to 33.2% in the first quarter. This reduction was the result of a more favorable product and customer mix in the first quarter compared to the fourth quarter. Our Thermal Products segment's component material cost remained fixed at 30% for both the fourth quarter of 2015 and the first quarter of 2016.
Another factor that contributed to the improved Q1 2016 gross margin was a reduction in the quarterly excess and off-fleet inventory charge, which declined from $110,000 in the fourth quarter to $70,000 in the first quarter.
Selling expense was unchanged at $1.3 million for the first and fourth quarter. Increased commissions and travel expenses in our Thermal Products segment were fully offset by reduced levels of salary and benefit expense in our Mechanical Products segment as well as reduced warranty claims and advertising expenditures. Engineering and product development expense was $991,000 for the first quarter compared to $905,000 for the fourth quarter, an increase of $86,000 or 10% sequentially. The increase primarily related to higher salary and benefit expense in our Thermal and Electrical Products segments.
General and administrative expense was $1.6 million for the first quarter, up from $1.5 million for the fourth quarter of 2015. Fourth quarter 2016 general and administrative expense included $99,000 worth of restructuring cost related to a reduction in force completed in our Mechanical Products segment in early January. When adjusted to remove this item, first quarter G&A expense increased $29,000 or 2% sequentially. This increase was related to increased salary and benefit expense, which was partially offset by reductions in professional fees.
Other income was $29,000 for Q1 compared to $5,000 for the fourth quarter. The $24,000 quarter over quarter increase in other income was primarily the result of foreign exchange transaction gains in the first quarter compared to foreign exchange transaction losses in the fourth quarter.
We accrued an income tax expense of $43,000 in the first quarter compared to a benefit of $187,000 accrued in the fourth quarter. Our effective tax rate was 35% in the first quarter compared to 121% benefit in the fourth quarter. The tax benefit booked in Q4 was driven by the operating loss as well as accruing the full year impact of the R&D tax credit that was permanently enacted during the fourth quarter of 2015, while our effective tax rate in Q1 2016 is a more normalized level. At March 31, 2016, our deferred tax assets were $1.2 million and our remaining net loss carry-forwards were $1.5 million for domestic state, primarily California, and $467,000 for foreign related to our German operations. We expect our effective tax rate for 2016 to be in the range of 34% to 36%.
First quarter net income was $81,000 or $0.01 per diluted share compared with fourth quarter net income of $33,000 or $0.00 per diluted share. Diluted average shares outstanding were 10,404,000 at March 31. We initiated our stock buyback on December 1, 2015 and during the quarter ended March 31, 2016 we repurchased 114,688 shares at a net cost of $468,000 or $4.08 per diluted share. As of April 29, 2016, we have repurchased a cumulative total of 205,603 shares or just under 2% of our outstanding common stock at a net cost of $821,000 or $3.99 per share.
Amortization and depreciation expense was $159,000 for the first quarter and EBITDA was $273,000 up from $15,000 for the fourth quarter.
Consolidated headcount at the end of March, which includes temporary staff was 115, down 11 from the level we had at December 31. As we noted during our last earnings call we reduced the annual operating expenses of our new EMS division, through the headcount reduction of 8 staff in early January 2016. We incurred approximately $99,000 in severance cost associated with this headcount reduction which was in addition to the headcount reduction of 5 staff in our Mechanical Products segment completed in July 2015. The remaining Q1 2016 staff reduction occurred in our Thermal Products segment.
I will now turn to our balance sheet. Cash and cash equivalence at the end of the first quarter were $25.0 million down $759,000 from December 31. We currently expect cash and cash equivalence to increase again starting in the third quarter of 2016 excluding the impact of any potential acquisition.
Accounts receivable increased by $941,000 to $5.3 million at March 31, driven by higher levels of shipments during the first quarter. Inventory decreased slightly by $66,000 to $3.5 million at March 31 and capital expenditures during the first quarter were at $38,000 down from $54,000 in the fourth quarter and represented new computer hardware related to a company-wide system upgrade.
Bob provided consolidated and segment revenue and booking data earlier. The backlog at the end of March was $3.5 million, up from $2.4 million at the end of December.
In terms of our financial outlook as noted in our earnings release we expect that the net revenue for the quarter ended June 30, 2016 will be in the range of $9.5 million to $10.5 million and that net earnings will range from $0.03 to $0.07 per diluted share. We currently expect that our Q2 2016 product mix will be more favorable than Q1 and that the second quarter gross margin will range from 48% to 50%. Operator, that concludes our formal remarks and we can now take questions.